The House was in session at the Capitol on Thursday, but thanks to the latest procession of Republicans reporting for duty in front of a Manhattan criminal courthouse to show support for former President Donald J. Trump at his trial, the party risked ceding its control of the floor.

Almost a dozen House Republicans showed up at the courthouse on Thursday, including hard-right rabble rousers like Representatives Matt Gaetz of Florida; Anna Paulina Luna of Florida; Lauren Boebert of Colorado; and Representative Bob Good of Virginia. They said they were there to speak on behalf of Mr. Trump because a gag order has barred him from speaking for himself.

“We are here of our own volition, because there are things we can say that President Trump is unjustly not allowed to say,” Mr. Gaetz said at a news conference outside the courthouse. He said the former president was on trial for a “made-up crime” that he called “the Mr. Potato Head of crimes” — composed of unrelated elements awkwardly stuck together.

Mr. Good said the trial was an example of Democrats trying to “rig” the presidential election against Mr. Trump. After Ms. Luna sat in the courtroom, she came out to report that: “The president is doing well. He’s in good spirits.”

Republicans control the House by such a slim margin, 217-213, that just two defections can sink legislation if all members are present and voting — and just a few absences can erase their majority altogether. The show of support for Mr. Trump from such a large group of members meant that for much of Thursday, the G.O.P. may have handed the floor over to Democrats, leaving themselves exposed on the House floor.

House Republicans had a vote scheduled for Thursday afternoon to rebuke President Biden for his decision to pause an arms shipment to Israel and compel his administration to quickly deliver weapons.