GOP senators, led by Majority Leader Mitch McConnell, have the power to veto the agenda of a changing America.Aaron Bernstein / Reuters

Even if Democrats regain unified control of the White House and Congress in 2020, the fate of their ambitious legislative agenda will still likely hinge on a fundamental question: Do they try to end the Senate filibuster?

If the party chooses to keep the filibuster, it faces a daunting prospect: Democrats elected primarily by voters in states at the forefront of the country’s demographic, cultural, and economic changes will likely have their agenda blocked by Republican senators largely representing the smaller, rural states least touched by all of those changes. In fact, since the Senate gives each state two seats, the filibuster allows Republican senators from states representing only about one-fifth of the country’s population to be in a position to stymie Democratic legislation.

Although the Democratic 2020 contenders are promising sweeping action on issues ranging from gun control to immigration, none of those proposals has any realistic chance of becoming law if the Senate rules requiring 60 votes to break a filibuster remain in place. “The argument over the filibuster really crystallizes if you actually win and you look out at the coming year,” says Adam Jentleson, who served as deputy chief of staff to former Democratic Senate Leader Harry Reid. On most issues, “you cannot count to 60 [votes], period. It becomes a very clear question of, Are we going to get anything done or not?

Such considerations led Reid, in a striking op-ed last week, to urge Democrats to abolish the filibuster when they regain power—and led Senate Majority Leader Mitch McConnell to respond with an op-ed of his own defending the rule.

Democrats and Republicans alike have become more frustrated with the filibuster as the Senate has grown more polarized since the 1980s. While defenders of the procedure have portrayed it as a mechanism that forces the majority party to negotiate with the minority party, in contemporary Washington, both parties have found it difficult to attract much support from the other for their initiatives under any circumstance. As a result, the filibuster has become simply a means for the minority to block the majority, rather than a spur to compromise.

That led Democrats, when they controlled the Senate in 2013, to eliminate the filibuster for nominations by the president, with the exception of Supreme Court picks. Republicans then swept away that exception in 2017. But both sides have hesitated at taking the momentous next step of eliminating the filibuster for all legislation.

Yet the widening demographic and geographic divide between the two parties is guaranteed to heighten the pressure on Democrats to make that move if the 2020 election provides them with unified control in Washington. In both the Senate and Electoral College, Republicans rely heavily on heartland states that have a large number of white Christians, rural populations, few immigrants, strong gun cultures, and major economic ties to the fossil-fuel economy. Democrats do better in states with fewer white Christians, more racial minorities and immigrants, a more urbanized population, fewer guns, and an economy less focused on fossil fuels.

There are exceptions on each side. Big, diversifying Sun Belt states—namely North Carolina, Florida, Georgia, Texas, and Arizona—still lean Republican, although all but Florida are growing more competitive for Democrats. And Democrats are still favored or competitive in several Midwest and northern states—including Minnesota, Michigan, Wisconsin, Vermont, New Hampshire, and Pennsylvania—that have relatively few immigrants and strong gun cultures.

But the basic pattern is clear. Democrats represent what I call the “coalition of transformation”: the group of voters most comfortable with the big changes remaking America. Republicans represent the “coalition of restoration,” centered on the predominantly white voters uneasy with those changes.

If Democrats take back the Senate, preserving the filibuster amounts to providing the places most resistant to America’s changes a veto over the agenda of the Democratic coalition based in the places that are most welcoming to them. In a Senate controlled by Democrats, the filibuster would effectively empower what America has been over what it is becoming.

“More and more Democratic activists are picking up on the fact that the filibuster, either by purpose or unintended consequences, is benefiting a certain amount of small-population states,” says Jim Manley, a former top aide to Reid and late Senator Ted Kennedy of Massachusetts. “There’s an inherent unfairness to the Senate that more and more people are focusing on.”

That structural imbalance is most apparent when looking at four issues near the top of the priority list for most 2020 Democratic contenders: gun control, immigration, climate change, and democratic reform. Gun control may be the most pointed of the four. Polls consistently show that roughly 90 percent of Americans support a requirement for universal background checks on all gun sales, including those at gun shows and on the internet. After the mass shootings in El Paso, Texas, and Dayton, Ohio, support for an assault-weapons ban has crossed 60 percent in several recent surveys.

Yet such measures have essentially no chance of passing the Senate, because so many Republicans representing states with strong gun cultures feel little pressure to respond to that national majority. Gun ownership by state is difficult to quantify precisely, but one study from 2015 ranked states on the share of residents who owned guns. In 19 states, the researchers found, at least 35 percent of the adult population owned guns. Republicans now hold 27 of the 38 Senate seats from those states. In another 10 states, at least 30 percent of the population owned guns, and Republicans hold 17 of those 20 seats. Democrats hold 33 of the remaining 42 seats in the 21 states where less than 30 percent of the population owns guns.

But those 21 states with the lowest rates of gun ownership contain well over twice as many people as the 19 states with the highest rates. In fact, their population (176 million) is substantially larger than all 29 states where at least 30 percent of adults own guns (147 million). But the Republican dominance in those states with lots of gun owners easily gives them enough votes to sustain a filibuster against any gun-control measure. That prospect leads Dan Pfeiffer, who was the White House communications director under President Barack Obama, to predict that gun control is the issue most likely to ignite a demand to end the filibuster, “because it is so urgent, has so much public support, and is the perfect example of why the filibuster is antidemocratic.”

Similar dynamics govern the prospects for action on climate change. Polls show that a majority of Americans believe that the climate is changing, that human activity is a contributor, and that the federal government should do more to respond. But what I’ve called a “brown blockade” in the Senate makes it virtually impossible for any meaningful climate action to overcome a filibuster.

Republicans now hold 35 of the 40 Senate seats in the 20 states that emit the most carbon per dollar of economic activity, which are mostly heartland states that are large energy producers, large manufacturers, or both, according to government figures. Republicans also hold 12 of the 20 Senate seats from the next 10 states that emit the most carbon per dollar. Democrats control 34 of the 40 seats from the 20 lowest-emitting states, most of which are coastal and have transitioned toward a greater reliance on renewable power. But once again, the Republican strength in the higher-emitting states gives the party the numbers to filibuster almost any climate initiative.

Immigration presents the same picture. For years, polls have found that about two-thirds or more of Americans support a comprehensive plan that would provide a pathway to citizenship for undocumented immigrants without a criminal record, while tightening enforcement at the border. In both 2006 and 2013, Democrats attracted enough Republican votes to cross the 60-vote threshold and pass comprehensive immigration reform. (Each time, the GOP-controlled House refused to consider the measure.) But after Donald Trump’s success at making the GOP more nativist, it’s not clear that enough Republicans would again join a narrow Democratic majority in 2021 to pass such legislation.

That’s especially true because, when it comes to immigration, once again, Republicans overwhelmingly represent the parts of America least touched by change. Forty-five of the 53 Republican senators represent the 30 states with the smallest share of foreign-born residents in their population, according to census figures. Democrats hold 32 of the 40 seats in the 20 states with the highest share of immigrants. And among those few Republicans in high-immigrant states, GOP senators in Arizona and Colorado, and more distantly Texas, will be among the Democrats’ top targets in 2020.

The tensions on these issues would be compounded for a Democratic Senate majority come 2021 because they largely align the same states on each side of the divide. Of the 30 states that emit the most carbon per dollar of economic activity, 26 also rank in the bottom 30 for immigrant population. Twenty-three of the high-carbon states also rank in the top 29 for gun ownership.

In all, 20 states meet each of these thresholds as high-carbon, low-immigrant, and high-gun places: Wyoming, Montana, Utah, North Dakota, South Dakota, Kansas, Oklahoma, Iowa, Indiana, Wisconsin, Kentucky, West Virginia, Tennessee, Louisiana, Arkansas, Alabama, Mississippi, South Carolina, and Alaska.

Of the 40 Senate seats across these states, Republicans now hold 36 of them, which comes close to the 41 votes needed to sustain a filibuster on any of these issues. Republicans also hold all four Senate seats in two other solidly GOP states that meet the criteria for low immigration and high carbon output, but not high gun ownership—Nebraska and Missouri. At that point, Republicans from the states least touched by change would need only a single vote from any other senator to reach the 41-vote threshold required to sustain a filibuster. That means that even if Democrats recapture unified control of government, they face the real threat that the same states, many of them smaller and disproportionately white and Christian, could block almost all of their goals—even though these 22 states contain only about 70 million people, only about one-fifth of the national population.

This equation isn’t likely to change much in 2020: Iowa and possibly Montana are the only states among those 22 with Senate seats up for grabs that Democrats have a serious chance to contest, and Democrats face a tough challenge to Senator Doug Jones of Alabama.

“The filibuster isn’t just enforcing the views of the minority in the sense that they have fewer seats; it’s enforcing the views of the minority in the sense that they represent a minority of the overall United States population,” Jentleson told me. “You are going to have Republicans who have fewer seats and represent a lot less than half the population using the filibuster to block changes that are favored by not just the party in power, but the broad majority of Americans.”

The same pattern is evident in Democrats’ attempts to expand access to democracy. House Democrats have already passed a series of ambitious voting reforms this year. These measures, which include a reauthorized federal Voting Rights Act and a mandate that states provide same-day voter registration, are meant to reverse voting restrictions passed in many Republican-controlled states. But the filibuster looms as a likely hurdle for any such legislation, partly because the GOP states that have passed those restrictions have elected to the Senate so many Republicans hostile to federal intervention in voting laws: The 20 states that political scientists have identified as imposing the tightest restrictions on voting have elected 30 GOP Senators.

Some Democrats, including several 2020 aspirants, are talking about going further than the House bill to add the District of Columbia and Puerto Rico as states. Such ideas would have no chance of beating a filibuster. Likewise, the pledges by most Democratic presidential candidates to propose legislation codifying a legal right to abortion—as concerns grow that the five Republican-appointed Supreme Court justices might overturn Roe v. Wade—would be doomed in a Senate that preserves the filibuster.

Many Democrats, especially those in the Senate, are hesitant about ending the filibuster if they indeed get the chance. Only a few of the 2020 candidates have urged its elimination, Senator Elizabeth Warren of Massachusetts most forthrightly. The hesitation partly reflects a respect for tradition. But Democrats also fear forging a weapon that could soon be used against them. And in fact, recent history suggests that Senate majorities are fragile: Neither party has controlled the Senate for more than eight consecutive years since 1980, the longest period of such instability since the turbulent decades immediately after the Civil War. “If you play the long game, there is no guarantee the Democrats are going to control the Senate for any length of time,” Manley told me. “We could be in a period where the Senate keeps on flipping back and forth; when one party gets the majority, they are just going to try to undo what the previous party did.”

Of course, there’s no guarantee that even after eliminating the filibuster a narrow Democratic majority in the Senate could summon the necessary 51 votes to pass legislation such as banning assault weapons or limiting carbon emissions, much less imposing a single-payer health-care system. But the pressure to try may become unavoidable, particularly because the 2020 election is likely to so starkly widen the trench between the two parties’ coalitions. “I think we are at a breaking point,” Manley said. “And I wouldn’t be surprised if the rules of the Senate changed sooner rather than later. More and more people are realizing how the filibuster does in fact protect a small number of states that don’t necessarily reflect the country as a whole.”

Jentleson likewise thinks that the demands for ending the filibuster could grow irresistible if Democrats win unified control and find a Republican Senate minority blockading any element of their agenda that can be filibustered. Especially after Republicans in this century have already twice won the White House while losing the popular vote, he says, “it’s not good for a democracy long-term for the agenda of the government to be consistently set by a minority of the population. It’s not sustainable.”

If the 2020 election fulfills all of the Democrats’ hopes, nothing may shape the results of their governance more than whether 50 Democratic senators agree with that assessment—and vote to end the filibuster in 2021.

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