WASHINGTON — In February 2016, while Donald Trump was busy sweeping the Republican presidential field, Sen. Mike Lee, R-Utah, led a group of conservatives in launching the Article 1 Project (or A1P) — an initiative urging members of Congress to reassert their powers under Article 1 of the Constitution. “Congress has delegated too much of its legislative authority to the executive branch … taking up a new position as backseat drivers of the republic,” Lee and then-Rep. Jeb Hensarling, R-Texas, wrote at the time, “we have moved from a nation governed by rule of law to one governed by the rule of rulers.” Item No. 1 on A1P’s agenda? “Reclaiming Congress’s power of the purse.”

Today, Congress’s power of the purse is being undermined by a Republican president. For the first time since Congress enacted the National Emergencies Act in 1976, a president has used his emergency authority to appropriate funds for a policy priority after Congress specifically refused to do so legislatively. This is not simply circumventing Congress. It is a direct assault on Congress’s Article 1 powers — exactly the kind of unprecedented abuse of power that A1P was created to fight against.

One would think that constitutional conservatives would be leading the fight in the Senate to reverse the president’s extraordinary emergency declaration and reclaim Congress’s power of the purse. So far, that’s not happening. Instead, we’re seeing plenty of excuses, with Republicans arguing that what the president is doing is technically legal, even if he should not have that kind of power.

Sorry, that’s a cop-out. Even if one thinks the emergency declaration is technically legal — and that is a point of debate among legal scholars — the law also provides Congress a mechanism to terminate an emergency declaration that it deems inappropriate. Why would any Republican not vote to use the express authority Congress granted itself under the law to do so?

Some Republicans are talking about amending the National Emergencies Act to have all emergencies end automatically in 30 days unless Congress votes affirmatively to extend the emergency — shifting power back from the executive to Congress. Fair enough. But up until now, such a law has not been necessary, because no president has abused his powers under the National Emergencies Act.

Almost all of the 59 previous emergency declarations have been to impose sanctions or trade restrictions on terrorists or other enemies. In the more than four decades since the act was passed, only twice has an emergency declaration been used to reallocate funds — and both instances were to carry out wartime construction projects, one related to the 1991 Persian Gulf War and one related to military response following the attacks of Sept. 11, 2001. So, it was not until Trump’s unprecedented abuse of the act that a constitutional crisis emerged.

Congress can debate whether the act should be amended in light of that abuse. But that does not absolve individual members of their responsibility to address this specific abuse of power. Some object that a vote on the resolution of disapproval is little more than a “show vote” because the president will veto it and it lets Democrats pretend that they care about separation of powers without doing anything real to address the problem. But it is within the GOP’s power to make sure the resolution passes with a veto-proof majority, which would make it the opposite of a “show vote.”

Nor is a vote to reverse the president’s executive overreach a vote against building the wall. The fact is, the president does not need an emergency declaration to build a border wall. He can reprogram an additional $4.6 billion from Treasury Department’s drug forfeiture fund and the Defense Department’s drug interdiction program without one. Together with the $1.38 billion Congress just appropriated, that gives him nearly $6 billion in immediate wall funding. That is more than he requested from Congress to begin with.

Republicans understandably feel a political imperative to support their president. But they also have constitutional and institutional imperative to reverse this abuse of power by voting “yes” on the resolution of disapproval. Were Barack Obama doing what Trump is doing, they would be united in opposition. If they care at all about preserving their Article 1 powers, senators are going to have to stand up to the president, the consequences be damned.

Thiessen, a Washington Post Writers Group columnist, may be reached at @marcthiessen on Twitter.