Trump made fun of Rep. Mark Sanford again. The House Freedom Caucus has had enough.

Rep. Justin Amash’s (R-MI) shouting could be heard through a closed door in the hallway of the Rayburn House office building on Monday night.

For the greater part of an hour, more than a dozen of the House’s most conservative lawmakers, and President Donald Trump’s most ardent defenders in the House Freedom Caucus, had been discussing immigration and other policy priorities.

Then Amash saw a tweet: President Donald Trump was on stage at a rally in South Carolina maligning Rep. Mark Sanford (R-SC) again. Sanford, a fellow Freedom Caucus member and well-liked member of the House Republican conference, was the second House Republican to lose a reelection primary under Trump earlier this month. The difference with Sanford was that Trump endorsed his primary challenger, Katie Arrington, just hours before the polls closed — a move that caught House Republican leaders by surprise.

“The president is in South Carolina, 100 miles from the district, speaking on the gubernatorial race and for some reason decided to tee off on me again,” Sanford said, leaving the Freedom Caucus meeting Monday. “So this is the fourth time, so this is why Justin brought that up.”

“What’s more important?” Amash could be heard asking, giving his colleagues what many conservative lawmakers have increasingly seen as an impossible choice: defending Trump — even when he lies or bullies a well-liked colleague — or standing up for what’s right?

Sanford, a perennial Trump critic, has become the president’s latest punching bag on Twitter and in private and public speeches.

Most recently, Trump tweeted a bold-faced lie about a recent visit with congressional Republicans, falsely claiming lawmakers cheered when the president made fun of Sanford during a closed-door meeting. The room actually fell silent when Trump mentioned Sanford, several Republican lawmakers in the room confirmed.

Freedom Caucus Chair Rep. Mark Meadows (R-NC) said the group would respond to Trump’s latest comments at the South Carolina rally.

“Everybody in there is very supportive of Mark Sanford, and I think that’s one of the things that overwhelmingly they believe that the president is getting bad political advice,” he said, saying he has identified who that adviser is.

But the entire episode is telling of increasing tensions between Trump and House Republicans; the vast majority of congressional Republicans, particularly in the Freedom Caucus, have defended Trump through every scandal, gaffe, and policy misstep. Some even found a way to spin Trump’s comments on Sanford.

“This president has done so many good things for this country, and to take that instance, as unfortunate as it is, [doesn’t] look at the positives that he has done,” Rep. Ralph Norman (R-SC) said in response to Trump’s tweet lying about Republicans’ reaction to his attacks on Sanford.

Trump doesn’t stick with the Republican Party — he knows Republicans will stick with him.

“Some people say I have the greatest political instinct in 50 years,” Trump said on stage in South Carolina, after mocking Sanford’s 2009 extramarital affair on stage.

Now those instincts are making trouble for his most ardent defenders in Congress.