This story has been updated with more Republican reaction to the news.

The firing of special counsel Robert S. Mueller III has long been a red line for most Republicans in Congress who are trying to work with their president.

But it's a red line they'd rather not act on — and now, with news that President Trump actually made moves to do it, they may be forced to.

There are two bills in Congress, both of which have some Republican support, that would protect Mueller from being fired by Trump. But neither bill has been seriously considered by leadership.

Up until this point, Republicans had given Trump the benefit of the doubt that he wouldn't launch a constitutional crisis. From their perspective, why take action and cause a confrontation with the president (and jeopardize their agenda) if they don't absolutely have to?

Now they may have to.

Trump moved to fire Mueller in June, shortly after the special counsel took over the investigation of Russia meddling in the 2016 election, the New York Times, then The Washington Post, reported on Thursday night. Trump seemed pretty dead set on it, and only backed off after the White House's top lawyer, Donald McGahn, threatened to resign.

Reports that Trump wanted to get rid of the special counsel don't entirely come out of the blue — he's frequently complained this investigation is a “hoax” and suggested it's politically motivated. There has also been evidence that Trump was toying with the idea of first firing Attorney General Jeff Sessions. He even hinted in a July interview with the New York Times that he'd fire Mueller if the independent investigation started looking into his finances.

Firing Sessions is one of the clearest paths for the president to get rid of the special counsel, who technically answers to the Justice Department. And that got some Republicans' attention.

“There will be holy hell to pay,” Sen. Lindsey O. Graham (R-S.C.) warned Trump via reporters in July of what would happen if the president fired Sessions. A few weeks later, two pairs of bipartisan senators unveiled legislation to protect Mueller if Trump tried to fire people in the Justice Department in a way that would eventually lead to getting rid of Mueller.

Even some of Trump's biggest Republican critics in the Senate didn't believe he'd go that far. “I can't imagine any administration taking a move like that,” Sen. Bob Corker (R-Tenn.) told reporters in October.

But this revelation is more concrete than news over the summer. Trump didn't just think about firing Mueller, he moved to do it. According to The Post's Rosalind Helderman and Josh Dawsey, discussions were had and meetings were held by his aides to try to get him to back off.

Republicans in Congress may not have been privy to any of the internal White House conversations at the time about the firing of Mueller, which could be one reason they backed off passing protections for the special counsel.

“I don’t hear much pressure to pass anything,” Senate Majority Leader Mitch McConnell (R-Ky.) told MSNBC in November. “There’s been no indication that the president or the White House are not cooperating with the special counsel.”

“I’ve never been convinced they’re constitutional,” Sen. John Neely Kennedy (R-La.), told The Post of one proposal requiring a three-judge panel to review any firing from the executive branch.

Or, they just might not be interested in a confrontation with the president. Sen. Thom Tillis (R-N.C.) signed onto Democratic legislation this summer to protect Mueller. But on Friday, the Daily Beast's Betsy Woodruff reports he's stopped trying to lobby his colleagues to do it. Trump may have wanted to fire Mueller in June, but that was June: "[T]he chatter that the administration is considering removing Special Counsel Mueller has completely come to a halt," Tillis spokesman Daniel Keylin told the Daily Beast.

There is no serious bipartisan bill to protect Mueller in the House of Representatives either, where some vocal Republican lawmakers are instead saying Mueller should step down because of what they allege are various levels of bias.

Democrats involved in Congress's Russia investigation were so worried by Republicans' shrugs about protecting Mueller that in December Sen. Mark R. Warner (D-Va.), the top Democrat on the Senate Intelligence Committee, gave a speech warning a “constitutional crisis” would happen if Trump fired Mueller while Congress was gone.

The debate in Congress probably won't immediately shift to how to protect Mueller. Instead, it will probably zero in on whether it's Congress's job to do it in the first place. “I believe now that this revelation has been made public, that there will be increasing pressure to protect Mueller,” moderate Rep. Charlie Dent (R-Pa.) told my Post colleagues.

But either way, the confrontation with the president that Republicans were trying to avoid has just landed on their doorstep.

Correction: There are currently bills in the House of Representatives to protect Mueller, but none of them appear to have significant bipartisan support to be viable.