Senate Majority Leader Mitch McConnell (R-Ky.). (Alex Wong/Getty Images)

"I DON'T HEAR much pressure to pass anything," Senate Majority Leader Mitch McConnell (R-Ky.) said in November when asked about bills that would protect special counsel Robert S. Mueller III should President Trump try to fire him. "There's been no indication that the president or the White House are not cooperating with the special counsel," Mr. McConnell explained.

Now there is an indication, and a pretty strong one. The New York Times reported and The Post quickly confirmed Thursday that the president moved to fire Mr. Mueller in June, shortly after the special counsel's appointment. Mr. Trump pulled back only after White House Counsel Donald F. McGahn threatened to resign.

Though it is unclear what motivated Mr. McGahn to resist, the White House counsel deserves credit for preventing a constitutional crisis. It's the second revelation in a week of a senior federal officer pushing back against the president's desire to fire law enforcement officials he deemed insufficiently loyal. That Mr. Trump pressed for these dismissals while his associates and possibly he himself were under investigation raises the question of obstruction of justice.

Meanwhile, all the members of the president's staff who baldly lied to reporters about whether Mr. Trump contemplated firing Mr. Mueller have surrendered even more dignity — and once again made clear that official White House assertions, from the president down, cannot be taken at face value. For his part, Mr. Trump flicked away the reports as "fake news," despite several news organizations' independent confirmation of the story.

With Mr. Trump's desire to fire Mr. Mueller now more than speculative, Congress must finally take action. Senators already have two bipartisan bills before them that would insulate the special counsel from the president's pique. One would require Justice Department officials to get judicial permission to fire a special counsel. The other would allow special counsels to challenge their termination before a judicial panel. Both raise constitutional questions about whether Congress can intervene to this degree in executive branch hiring and firing. But the bills' authors have expressed willingness to adjust their legislation to minimize constitutional concerns.

Moreover, the point is not merely to erect legal protections for Mr. Mueller, although that would be a welcome result. Passing such a bill would demonstrate bipartisan unity in Congress against presidential meddling in the Mueller probe, which, it must not be forgotten, concerns the election-year attack on the United States by a hostile foreign power — and any assistance rendered by complicit Americans.

Even if the courts eventually deemed the measures unconstitutional, their existence would raise at least temporary barriers to firing Mr. Mueller. And even if the bills never became law, perhaps because of a presidential veto, it would at least be clearer to Mr. Trump that any move against the special counsel would elicit a backlash far greater and more damaging than the outcry that chastened him after he fired FBI Director James B. Comey.

Congressional leaders' excuses for inaction have evaporated. It is time for them to choose: party or country?