Last week Donald Trump willfully violated the Constitution as even he once understood it, despite being warned against doing so by dozens of members of Congress.

Hours before the president ordered the U.S. military to strike three targets in Syria, 88 members of Congress sent him a letter to remind him of his legal obligations. Strikes “when no direct threat to the United States exists” and “without Congressional authorization” would violate the Constitution’s separation of powers, they declared. “We strongly urge you to consult and receive authorization from Congress before ordering additional use of U.S. military force in Syria.”

That account of the law was bipartisan: The signatories included 15 Republicans and 73 Democrats, and a similar letter sent to President Obama in 2013 was signed by 119 Republicans and 21 Democrats. Surveying all the legal rationales offered in Trump’s defense, Jack Goldsmith and Oona Hathaway conclude at Lawfare, “there is no apparent domestic or international legal authority for the strikes.” And crucially, Trump himself explicitly shared their understanding of the law.

As he put it in 2013:

Here’s another example:

Today’s Republican-controlled Congress lacks a majority willing to punish Trump for his flagrantly illegal war-making. And that status quo alarms many. “This country now considers it perfectly normal for the president to launch a fierce assault against a foreign country 5,000 miles from our borders without any congressional involvement at all, let alone a declaration of war,” the commentator Damon Linker observed. “It’s just what presidents do, whenever they want.”

“If Congress does nothing to challenge the president’s illegal attack,” Daniel Larison warns, “they will be accepting own irrelevance in matters of war from now on.”

Yet there is a minority faction that wants to restore the Constitution.

“These offensive strikes against Syria are unconstitutional, illegal, and reckless,” Representative Justin Amash, a Michigan Republican, said. “The next speaker of the House must reclaim congressional war powers as prescribed in Article I of the Constitution. Speaker Ryan has completely abdicated one of his most important responsibilities.”

Members of the Senate have spoken up too. Prior to the strikes, Senator Rand Paul contested the notion that the president was constitutionally empowered to launch them.

And Democrats weighed in after the strikes, as well. “Trump’s decision to launch airstrikes against Syria without Congress’s approval is illegal,” Senator Tim Kaine said. “We need to stop giving presidents a blank check to wage war. Today it’s Syria, but what’s going to stop him from bombing Iran or North Korea next?”

“While Bashar al-Assad must be held accountable for his unlawful use of chemical weapons against civilians, the strikes that are being carried out are being done without an authorization from Congress, which is unacceptable,” Senator Bob Casey said. His colleague Bernie Sanders declared them “illegal and unauthorized,” while Senator Elizabeth Warren tweeted: “The Constitution gives Congress the power to authorize military action. If @realDonaldTrump wants to expand American military involvement in Syria’s civil war, he must seek approval from Congress – & provide a comprehensive strategy with clear goals & a plan to achieve them.”

Reasserting congressional control over war-making is substantively important.

First, the status quo undermines democracy. Voters casting their ballots in the 2018 midterms ought to be able to look to an up-or-down vote to determine where their representative stood on striking Syria, one of the most grave and consequential matters that the country has considered over the last couple of years. Instead, legislators escaped taking a stand, rendering voters unable to hold them accountable.

Second, as Tim Carney writes, it is corrosive to the rule of law “for a president to go to war through unconstitutional means,” and “the precedent of previous presidents’ illegal, unauthorized wars doesn’t make Trump’s unauthorized war legal.”

Third, as the law professor Ilya Somin points out, some of the prudential reasons that caused the Framers to vest the war power in Congress are even more relevant today:

Their greatest concern was ensuring that no one person would have the power to take the nation to war … This is an even more serious danger in an era when the Oval Office can be occupied by a dangerously impulsive and ignorant demagogue, thanks in part to the breakdown of political safeguards against such an eventuality. The Founders expected that such dangerous men would be kept away from the presidency by institutions such as the electoral college, which was supposed to exercise independent judgment and screen out demagogues. But, as early as the first contested elections in 1796 and 1800, it became clear that most electors would simply vote the party line.

In later periods, party elites exercised a similar screening function … That has obviously broken down in recent years, as the process has become more populist, leading to the election of Trump.The Founders’ fear that a president might launch a war to distract attention away from domestic political problems is also more plausible under modern conditions, where vivid 24-hour cable TV news coverage enables even a distant war to dominate public attention to a greater degree than was feasible two centuries ago.

If Hillary Clinton, one of the more hawkish politicians of her generation, was in the White House, there might be some prospect of Republicans reining in the war power. But because Donald Trump, a Republican, is in the White House, and because partisanship so often wins out over principle in Washington, D.C., the Democratic Party offers the best hope for restoring congressional control over the war power in the near future.

Its members are hardly united behind that goal. But a political incentive is there. After all, President Trump is on record having told Americans that congressional authorization would be needed to wage war in Syria. He also told his voters that he would stop pouring American money into the conflict. That makes him and his GOP supporters vulnerable on this subject.

In lots of competitive House races, the Democrat could profit with a message like this:

We all saw Donald Trump repeatedly tweet that bombing Syria without permission would be dumb and illegal. Then we watched him do it anyway as president. What will this unpredictable man do next? No one knows. His word is worthless. That’s why Congress needs to intervene: New wars must be put to a vote, not launched on a whim by an impulsive, hot-tempered gambler. Republicans have shown that they’ll basically let the president do what he wants, then go on television and defend him, whatever it is. I’ll fight to force him to get permission from Congress before he launches new wars—and I won’t sign off unless the people actually support risking more blood and treasure.

How many Democratic candidates would take a stand like that?

Absent leadership from Democrats, the work of exposing the illegality of Trump’s actions falls to critics outside the government. Spencer Ackerman reports on one such effort:

His administration has yet to declassify a legal memorandum, penned by the Justice Department’s Office of Legal Counsel around the time of last year’s Syria strike, that court papers describe as “advice and recommendations to the president … regarding the legal basis for potential military action.’ That memo is the subject of a Freedom of Information Act lawsuit from the Protect Democracy Project, a bipartisan group centering around Obama administration attorneys. On Monday, the group filed an emergency motion for its release, citing the “potentially imminent military action” in Syria flowing from its contents.

Americans elected the presidential candidate who promised to be less interventionist than 2000, 2008, 2012, and 2016. Insofar as Democratic candidates cling to the hawkish approach of their failed 2016 standard-bearer, they are giving away votes in 2018 and setting up the U.S. for more imprudent wars. Insofar as Republicans let Trump wage war where he likes, without a direct threat to America or congressional permission, they are on the wrong side of the Constitution.