In the next few years, many Americans understand, the Supreme Court may provide answers to some of the most hotly contested questions of constitutional law—the scope of affirmative action and federal power, for example, or the future of Roe v. Wade. What fewer recognize is that if the balance of the current Court changes, the settlement of these questions will not be part of the ordinary stream of decisions, but will instead represent the culmination of a more fundamental battle over the Constitution that has been waged since the New Deal era, one whose outcome could define American government and politics for many decades to come.

This is not the first battle over the Constitution in American history, but the fourth. All four battles have concerned the nature and scope of federal power in balancing the values declared to be self-evident in the Declaration of Independence: liberty, equality, and popular sovereignty. In this sense, the fourth battle echoes the three earlier battles and encapsulates the unique status of the Constitution in American life as the one document that both divides and unites us.

The first battle, fought from 1787 to 1791 over the proposal and ratification of the Constitution, concerned the nature and scope of federal power to raise funds for the common defense, to create a national economy, and to protect private property against mob violence. The second battle, fought during and after the Civil War, concerned the preservation of the Union, the extinction of slavery, and the promise of extending civil and political rights to African Americans. The third battle, fought over Franklin D. Roosevelt’s court-packing proposal in 1937, concerned the constitutionality of the Progressive-era and New Deal regulatory state and whether the Supreme Court should interpret the federal government’s power to regulate the economy broadly or narrowly. This included Congress’s power to delegate authority to the president and the president’s power to act unilaterally at home and abroad.

Ever since the third battle ended in the Supreme Court’s decision to uphold the post–New Deal regulatory state, conservatives and libertarians have insisted that by abandoning checks on congressional, executive, and judicial power, the Court betrayed the original meaning of the Constitution. Ushering in the fourth battle for the Constitution, Republican presidents since Ronald Reagan have pledged to appoint justices who would reverse the post–New Deal understanding of the Constitution and limit federal and judicial power by reining in the administrative state, overturning Roe v. Wade, and enforcing the ideal of a color-blind Constitution.

The election of 2020 may well resolve this fourth battle for the Constitution, which has been exacerbated during Donald Trump’s presidency by an unusual series of constitutional conflicts about the nature and scope of executive versus congressional power. Some of them—such as the challenges to the president’s travel ban and proposed addition of a citizenship question to the census—are being resolved by the Supreme Court. Others, involving the president’s contacts with Ukraine, could culminate, over the next year, in impeachment by the House and acquittal by the Senate. If Trump wins reelection and replaces a liberal justice with a conservative one, there will likely be five solid votes on the Supreme Court to revive the originalist Constitution; if a Democrat wins, the fourth battle will continue, perhaps resulting in a form of court packing, a Republican Senate’s refusal to confirm Democratic nominees, or other instances of extraordinary constitutional conflict.

Given these possibilities, it’s perhaps unsurprising that the public is highly focused on the Supreme Court and the Constitution. Americans today are more engaged by constitutional issues than at any other time since Roosevelt threatened to pack the Supreme Court. On the right, a quarter of Trump voters said that the future of the Supreme Court was the most important factor in their decision to support him in 2016. And Democratic voters are paying attention to the Supreme Court as well. Seven out of 19 Democratic presidential candidates, including Senators Elizabeth Warren and Cory Booker, have said that they are open to packing the Court to guarantee a liberal majority. Senate Democrats recently filed a Supreme Court amicus brief threatening that if the Court doesn’t drop a pending Second Amendment case, the justices will face a public reckoning in the form of court packing. “The Supreme Court is not well. And the people know it,” Senator Sheldon Whitehouse wrote in the brief. “Perhaps the Court can heal itself before the public demands it be ‘restructured in order to reduce the influence of politics.’”

In response to this crucial moment in the history of the Constitution and the United States, the National Constitution Center and The Atlantic are launching a new project, The Battle for the Constitution. Our goal is to convene the leading constitutional scholars in America—progressive, conservative, libertarian, or idiosyncratic—to write about the constitutional debates at the center of American life. Throughout the project, readers can also learn from the National Constitution Center’s Interactive Constitution and We the People podcasts, which bring together leading liberal and conservative scholars to explore every clause of the Constitution. The stakes of this battle are enormous, and we hope that the essays in this nonpartisan project will provide readers with the context, analysis, and perspective needed to make sense of it all. There is no better way to begin, perhaps, than reviewing the stakes of the previous battles.

The first battle for the Constitution, which took place between the Federalists and the Anti-Federalists from 1787 to 1791, was about the balance of the competing powers of the federal and state governments, the powers and size of the federal government, and the question of who, ultimately, should be sovereign: the people of each state or the people of the United States. The Federalists, led by James Madison and Alexander Hamilton, felt that the existing government under the Articles of Confederation was too weak to protect private property or public safety, and to preserve a workable union. Congress had so little power to raise revenue that it was unable to force the states to pay the debts to British creditors that they had incurred before the Revolutionary War, or to enforce the Treaty of Paris, which required the states to honor debts that some of them were refusing to pay. In Massachusetts, for example, the state legislature raised taxes and demanded that private debts be paid in hard currency—gold and silver—rather than in depreciated paper money, which resulted in a financial crisis for poor farmers across the state. Thousands of angry debtors, led by Daniel Shays, staged tax protests at courthouses that were imprisoning farmers, many of whom were veterans of the Revolutionary War, for nonpayment of debts. In January 1787, the mob attacked the federal armory in Springfield, Massachusetts, in a failed effort to seize its weapons and overthrow the state government.

Alarmed by this turbulence, Madison argued that a large republic would be less vulnerable than a small one would be to instability and passionate mobs. “A rage for paper money, for an abolition of debts, for an equal division of property, or for any other improper or wicked project, will be less apt to pervade the whole body of the Union than a particular member of it,” he wrote in “Federalist No. 10.” Madison and his fellow Federalists therefore set out to create a federal government large and strong enough to avoid the dangers of faction, which Madison defined as any group, whether a majority or a minority, animated by passion rather than reason and devoted to self-interest rather than the public good. To avoid these evils of faction, the new Constitution provided a strong but limited Congress divided between two houses, a unitary and nationally elected executive, and life tenure for judges. The new government was designed to be forceful enough to protect private property and provide for the common defense. But because its power was divided among different branches that could check and counteract one another, and between the states and the federal government, it was designed to be constrained enough to protect liberty and avoid tyranny.

The Anti-Federalists, led by George Mason, worried that the new central government would be far too powerful and threaten state sovereignty. In the novel invention of the presidency they saw what one of the delegates to the Constitutional Convention, Edmund Randolph, called “the foetus of monarchy,” a tyrant who might conspire with the aristocratic Senate to threaten liberty. Mason, who initially supported ratification of the Constitution, came to oppose it because of the broad scope of Congress’s power. In his widely circulated tract “Objections to the Constitution,” he warned that the clause giving Congress the power to pass all laws “necessary and proper” to achieve common purposes would allow it to create monopolies, reclassify certain acts as crimes, and generally “extend their powers as far as they think proper.” Most of all, he objected to the lack of a Bill of Rights. Like most Federalists, Madison originally argued that a Bill of Rights was unnecessary and potentially dangerous, since the Constitution itself did not authorize Congress to threaten liberty and enumerating a fixed list of natural rights might wrongly suggest that others were excluded. But after hearing Mason’s and the other Anti-Federalists’ objections during ratification, Madison eventually changed his mind and drafted what became the Bill of Rights, cutting and pasting from state constitutions, most notably Mason’s own Virginia Declaration of Rights of 1776.

But the Bill of Rights constrained only Congress, not the states. Madison, who sought unsuccessfully at the Constitutional Convention to give the new central government a “negative,” or veto, over state laws, was unable to win support for his favorite amendment, which would have prevented states from violating the rights of conscience, press, and trial by jury. All of these rights, of course, were disregarded by the states that maintained chattel slavery. The institution of slavery also violated the natural rights of equal liberty declared to be self-evident and unalienable in Thomas Jefferson’s Declaration of Independence, which was also influenced by Mason. In the 1770s and ’80s, five Northern states adopted policies to abolish slavery, and Madison said during the convention that he “thought it wrong to admit in the Constitution the idea that there could be property in man.” (Vermont, the first state to abolish slavery, in 1777, didn’t join the Union until 1791.) But the convention infamously refused to resolve the question, meaning that slavery would remain a central and shameful part of American law and life.

The second battle for the Constitution finally ended that sinful institution, opening up the possibility for African Americans to have equal liberty under the law. But the second battle did not begin as a crusade for liberty and equality; its origin, instead, was as a fight to protect the Union from the secession of Southern states. The uneasy peace between North and South had frayed during the 1850s. The Southern states had abandoned their devotion to states’ rights and invoked federal power to enforce laws such as the Fugitive Slave Act, which required the return to Southern bondage of enslaved people who had escaped to the North and freedom. This had the effect of radicalizing the North.

The first Republican Party platform was drafted in 1856 to preserve the Union and the principles of the Constitution and the Declaration of Independence, denying the power of Congress or any individual to maintain slavery in the federal territories. The following year, Chief Justice Roger B. Taney held in Dred Scott v. Sandford that black people had “no rights which the White Man was bound to respect,” that they could not be citizens of the United States, and that the Constitution required that all federal territories allow slavery. In the process, Taney struck down both the central principle of the Republican Party platform and the Missouri Compromise, which attempted to maintain the balance between free and slave states by banning slavery in the northern part of the Louisiana Territory. The North responded in 1860 by electing a Republican president, Abraham Lincoln. The South, in turn, responded with secession, attempting to leave the Union and form a new government, the Confederate States of America.

The Civil War began as a battle over the constitutionality of secession. The South argued that the Constitution, like the Articles of Confederation, was nothing more than a league of sovereign states, and that the states remained unilaterally free to exit. Lincoln, invoking the Founder James Wilson, insisted that since we the people as a whole had created the United States, only the whole people could alter it. He therefore denied the constitutional authority of the Confederate states to leave the Union, instead declaring that those states had been overrun by rebels, and took extraordinary measures—most notably suspending habeas corpus—to suppress the rebellion.

Not until 1863 did the second battle for the Constitution shift its focus from preserving the Union to securing the rights of African Americans. On January 1 of that year, Lincoln issued the Emancipation Proclamation, an executive order declaring that “all persons held as slaves” in the rebel states “are, and henceforward shall be free.” (Lincoln’s order did not free enslaved people in the loyal border states or in parts of the Confederacy already under Northern control, which he believed to be beyond his constitutional authority to act out of military necessity as commander in chief.) And in November, at Gettysburg, Lincoln promised a “new birth of freedom” to fulfill Jefferson’s “proposition that all men are created equal.” In 1865, Lincoln’s second inaugural address consecrated the Civil War as America’s penance for the founding sin of slavery. And the Union’s military victory a month later led to the Thirteenth Amendment, which abolished slavery; the Fourteenth Amendment, which promised African Americans equal citizenship; and the Fifteenth Amendment, which promised African American men the right to vote.

The second battle for the Constitution culminated in a new understanding of the relationship between the Declaration of Independence and the Constitution. The Constitution both empowered the federal government to protect the natural rights of equal liberty identified in the declaration and also said that the federal government was the greatest threat to those rights. The Thirteenth, Fourteenth, and Fifteenth Amendments not only guaranteed rights, but also gave Congress the power to enforce them. In that sense, the Reconstruction Congress conceived of a new understanding of the Constitution in light of the Declaration, expanding the powers of the national government to protect the rights of the people.

The Reconstruction Amendments represented what some conservatives call a “Second Constitution” and some liberals a “Second Founding.” But they did not resolve the second battle for the Constitution. Many white Americans, particularly in the South, set out to nullify the promise of the Reconstruction Amendments. The result was what the South called Redemption, a concerted effort to undermine Reconstruction with terror, violence, and legal subversion. John Bingham, the principal framer of the Fourteenth Amendment, had drafted the amendment to expand Congress’s power to protect civil rights, and to require the states to respect the Bill of Rights. But in the 1873 Slaughterhouse Cases, the Supreme Court ignored Bingham’s original understanding and refused to apply the Bill of Rights against the states. In 1876, in United States v. Cruikshank, the Court neutered Congress’s ability to use the Fourteenth Amendment enforcement power to police racial terrorism by Southern whites against freedmen. The Compromise of 1877 put an end to Reconstruction, awarding the contested presidential election to the Republican candidate, Rutherford B. Hayes, in exchange for his promise to withdraw federal troops from the South. In the 1883 Civil Rights Cases, the Court struck down the landmark Civil Rights Act of 1875, the keystone of Reconstruction, holding that the Fourteenth Amendment’s prohibitions applied only to the states, not to private individuals.

And in 1896, the Court infamously upheld segregation itself, ruling in Plessy v. Ferguson that separate railway cars for blacks and whites didn’t violate the Constitution, because the Fourteenth Amendment “could not have been intended to abolish distinctions based upon color, or to enforce social, as distinguished from political, equality, or a commingling of the two races upon terms unsatisfactory to either.” In one of the most prophetic dissents in American history, Justice John Marshall Harlan insisted that “in view of the Constitution, in the eye of the law, there is in this country no superior, dominant, ruling class of citizens. There is no caste here. Our constitution is color-blind, and neither knows nor tolerates classes among citizens. In respect of civil rights, all citizens are equal before the law.” Fifty-eight years later, in 1954, Harlan’s dissent would inspire Thurgood Marshall when he argued Brown v. Board of Education. But for decades after the withdrawal of the Union army, the Court undermined Congress’s ability to check racial oppression in the South. The unwillingness of the justices to enforce the Reconstruction Amendments’ promise of equal political and civil rights allowed the South to flagrantly subvert African American voting rights and empowered racist mobs to rule by terror.

The third battle for the Constitution, like the first, concerned the balance between federal and state power over the growing economy. But it also concerned the growing powers of what the American historian Arthur Schlesinger called the “imperial presidency.” The rise of the Progressive movement at the turn of the 20th century—led by Republicans such as Theodore Roosevelt and Democrats such as Woodrow Wilson and Louis Brandeis—had led to increasing economic regulation by the states, much of it aimed at promoting economic equality and protecting the health, safety, and welfare of the working classes. The Court was skeptical, and struck down some of these economic regulations. In 1905, for example, the Court invalidated maximum-hour laws for bakers, in Lochner v. New York. But the Court generally upheld federal authority, with the exception of two cases striking down federal regulation of child labor, Hammer v. Dagenhart in 1918 and Bailey v. Drexel Furniture Co. in 1922.

Both Wilson and Roosevelt claimed that the president was a steward of the people who could rule directly in their name without congressional approval. And the election of Franklin D. Roosevelt in 1932 led to even more sweeping assertions of executive power, and to a more dramatic confrontation with the Court. In a sequence of decisions, the Court’s conservative wing—led by the so-called Four Horsemen: Justices Willis Van Devanter, James McReynolds, George Sutherland, and Pierce Butler—struck down the major pillars of the first New Deal. Most notably, in the 1935 case A. L. A. Schechter Poultry Corp. v. United States, the Court struck down the National Industrial Recovery Act as an unconstitutional delegation of power from Congress to the president. And in 1936, in United States v. Butler, the Court held that the Agricultural Adjustment Act exceeded Congress’s power under the commerce clause.

Following his landslide reelection in 1936, Roosevelt responded to the Court’s challenge with one of his own. Feigning concern for the justices’ workload as well as their advanced age, he proposed a court-packing scheme that would have expanded the Court to as many as 15 justices, offering retirement at full pay for all justices over 70 and creating a new seat for every justice over 70 who refused to retire. This would have allowed Roosevelt to appoint six new justices immediately, reshaping the Court and marginalizing the Four Horsemen. Both liberal and conservative justices made their opposition clear, including the progressive hero Louis Brandeis, and the plan was overwhelmingly defeated in Congress. But in the 1937 case West Coast Hotel Co. v. Parrish, decided just weeks after Roosevelt first announced his court-packing plan, Chief Justice Charles Evans Hughes and Justice Owen Roberts joined with the three liberal justices (Brandeis, Harlan Fisk Stone, and Benjamin Cardozo) to uphold Washington State’s minimum-wage law. Roberts’s decision to side with Roosevelt and the liberals was seen by many, fairly or not, as the “switch in time that saved nine”: By upholding the New Deal, the Court took the political wind out of the sails of court packing.

The Four Horsemen soon retired, and Roosevelt eventually appointed seven of the nine justices, elevating Stone to chief justice in 1941. The new Court dramatically expanded its interpretation of Congress’s powers to regulate the economy and delegate authority to the president in ways that both supporters and critics viewed as tantamount to a new understanding of the Constitution. In 1938’s United States v. Carolene Products, the Court made clear that it would generally defer to all economic regulations and view laws more skeptically only if they affected disadvantaged minorities or infringed on the Bill of Rights.  In 1941’s United States v. Darby Lumber Co., the Court upheld key provisions of the Fair Labor Standards Act, confirming that Congress could use its power over interstate commerce comprehensively to regulate the national economy. And in 1942’s Wickard v. Filburn, the Court essentially removed all limits on Congress’s power to pass economic regulations, upholding a federal law that prohibited farmers from growing wheat to feed animals on their own farms, on the grounds that growing their own wheat might lead them to buy less of the grain on the open market, thereby affecting interstate commerce.

The third battle for the Constitution was temporarily resolved when the Supreme Court embraced the constitutionality of the post–New Deal regulatory state. A generation later, President Lyndon B. Johnson would use the same New Deal precedents to persuade the Court to uphold the Civil Rights Act of 1964, in what some called a “second Reconstruction.” The Redemption-era Court had held that the Fourteenth Amendment did not empower Congress to regulate private discrimination. But in 1966, in South Carolina v. Katzenbach, Earl Warren’s Court held that if Congress could regulate wages and hours using its commerce power, it could rely on the same power to protect civil rights. Thus, the third battle for the Constitution allowed the civil-rights movement to sustain its landmark victories and fulfill the promise of the second battle.

Although Roosevelt and the New Dealers won a decisive victory over the Four Horsemen, not everyone agreed that the victory was constitutionally legitimate. As early as the 1940s, as the political scientist Ken Kersch argues in Conservatives and the Constitution, different strands of the conservative legal movement (including evangelical Christians, Roman Catholics, libertarians, and pro-business Hamiltonians) insisted that the presidential architects of the Progressive-era and New Deal regulatory state—most notably, Presidents Wilson and Franklin D. Roosevelt—had disregarded the natural-law limitations on government recognized in the Declaration of Independence and codified in the Constitution. Their criticisms broadened in the 1950s and ’60s during the era of the Warren Court, when they assailed decisions protecting the right to use contraception and upholding the rights of welfare recipients and criminals as inconsistent with natural law or with the limited powers for Congress, the courts, and the executive defined in the Constitution.

In 1968, President Richard Nixon won election largely by running against the liberal Warren Court on a platform of law and order. Twelve years later, Ronald Reagan won the presidency and brought with him to Washington a group of conservative lawyers preaching the gospel of constitutional originalism. The core premise was that the Court had distorted or disregarded the original meaning of the Constitution in order to accommodate modern liberal sensibilities. This betrayal of the original meaning had begun in the 1930s, when the Court upheld the exercise of congressional and executive power far beyond what the Framers had envisioned. And it continued in the 1960s, when the Warren Court invented, as the originalists saw it, a host of new rights not explicitly mentioned in the text of the Constitution. No case drew their ire more than Roe v. Wade, decided in 1973, which relied on an unenumerated right to privacy to hold that the Constitution protected the right to abortion.

Reagan’s presidency marked the beginning of the fourth battle for the Constitution. But Reagan fell one justice short of achieving a decisive victory soon after the fourth battle began. In 1986, when Reagan elevated William Rehnquist to chief justice, he appointed the originalist Antonin Scalia to replace him as an associate justice. One year later, when Justice Lewis Powell retired, Reagan nominated Robert Bork, at the time an even better-known originalist than Scalia, to replace Powell. Bork’s appointment would have given the conservatives a solid majority on the Court to rein in the expansive post–New Deal Constitution and return to the more limited pre-1937 vision of federal power. As Senate Democrats mobilized against Bork, his confirmation hearings became contentious to an unprecedented degree. The Democrats argued that Bork would overturn countless Supreme Court precedents from the post–New Deal and Warren era, including Roe.

Bork was ultimately defeated, and Reagan nominated instead the more moderate conservative Anthony Kennedy, who was confirmed with little opposition. In 1987, therefore, the originalists were denied their first chance to undo the post–New Deal expansion of federal power and resurrect their understanding of the original Constitution. The fourth battle for the Constitution, one that pitted the liberal defenders of the Warren Court against their conservative-originalist opponents, then settled into a protracted stalemate for the rest of Kennedy’s tenure.

The fourth battle, declared by the Bork hearings, has continued to simmer for more than three decades. Soon after Bork’s defeat, President George H. W. Bush nominated Clarence Thomas, the Court’s second originalist justice. Even more outspoken than Scalia, Thomas has consistently argued that many major constitutional developments since the New Deal have betrayed the Constitution’s original meaning and should be overruled. As Presidents George W. Bush and now Donald Trump have appointed more conservative justices, Thomas’s vision has come closer to achieving a Supreme Court majority.

With Kennedy’s retirement and the appointment of Justice Brett Kavanaugh to replace him—after a confirmation even more divisive than that of Bork or Thomas—Chief Justice John Roberts now holds the deciding vote on the Court. To his left sit four liberals, led by Justice Ruth Bader Ginsburg, the architect of the Court’s gender-equality jurisprudence as an advocate in the 1970s. To his right are four conservatives, led by Thomas, who are more committed to rethinking the scope of federal power under the commerce clause; in reviving the structural limitations of the Constitution, including the nondelegation doctrine, which would limit Congress’s power to delegate regulatory authority to the president; in striking down affirmative-action and voting-rights laws as violations of the color-blind Constitution promised by Justice Harlan; and in reorienting protections for individual rights away from sex and gender issues such as abortion and gay rights and toward increased protections for religious liberty and the right to bear arms.

Because of his concern for maintaining the nonpartisan legitimacy of the Court, Roberts has shown a reluctance to overturn the post–New Deal regulatory state. On the one hand, in the 2012 case National Federation of Independent Business v. Sebelius, Roberts joined with the liberals to uphold President Barack Obama’s signature Affordable Care Act as a tax, even as he agreed with the conservatives that the law’s individual mandate could not be sustained as an exercise of Congress’s power to regulate interstate commerce. On the other hand, Roberts wrote the opinion in the 2013 case Shelby County v. Holder, striking down a key feature of the Voting Rights Act of 1965. As long as Roberts sits at the center of the Court figuratively as well as literally, the originalist revolution is unlikely to achieve a clear victory and will chip away at the constitutional settlement of the third battle incrementally rather than decisively. The next year may also bring a series of constitutional confrontations over Congress’s power to check or oversee unilateral executive action, which could lead to unexpected ideological alignments among the conservative originalists and the liberals on the Court.

But Roberts may not hold the balance of power for long. If Trump is reelected, he will likely have the chance to replace at least one liberal justice with a conservative. That would put Kavanaugh at the center of the Court ideologically, with potentially dramatic results. Five justices are now considering reviving the nondelegation doctrine. Justice Elena Kagan wrote in Gundy v. United States in June that this could mean “most of government is unconstitutional.” A sixth vote would accelerate this revival of the originalist constitution, with significant consequences for the regulatory power of the federal government and the extent of congressional and executive authority. The fourth battle for the Constitution might well culminate in a series of transformative decisions that could meaningfully restrain the scope of federal power for the first time since 1937.

The uneasy status quo is now under pressure not only from the right, but also from the left. If a Democrat wins the presidency in 2020, he or she may not have a chance to replace a conservative justice in the next four years. A Republican Senate might even refuse to confirm any nominees by a Democratic president, precipitating what some would view as a constitutional crisis. And whether or not a Democratic president has a chance to replace a liberal justice, the Democratic Party views the Court’s legitimacy as compromised, most notably because of the Senate’s refusal to consider Obama’s nomination of Merrick Garland to replace the late Justice Scalia. That’s why several presidential candidates for the 2020 race have endorsed a modern form of court packing, promising to expand the Court to prevent the conservative majority from remaining in power indefinitely.

The constitutional stakes in the election of 2020, therefore, are as high as they were in the election of 1936. A conservative Court might strike down climate-change legislation in ways that could provoke a dramatic political backlash. Or the next few years might possibly see a progressive rather than a conservative majority on the Court, obtained through extraordinary means not attempted since the New Deal era. A new liberal majority on the Court might strike down the death penalty; expand the scope of affirmative action and campaign-finance regulation; and bring increased scrutiny to state electoral practices, including partisan gerrymandering and voter-identification laws. And a liberal Court might also entertain the notion of affirmative rights to health and welfare under the Constitution—for example, by hearing suits trying to force the government to act on climate change. More than 50 years have passed since the last progressive Court, and a new one might stake out a path that is hard to anticipate.

Either way, the future of the Constitution hangs in the balance as the fourth battle begins in earnest.