WASHINGTON — In a bitterly divided Congress, it was a rare measure that had been expected to sail through without a fight.

A bill to name a federal courthouse in Tallahassee after Justice Joseph W. Hatchett, the first Black man to serve on the Florida Supreme Court — sponsored by the state’s two Republican senators and backed unanimously by its 27 House members — was set to pass the House last month and become law with broad bipartisan support.

But in a last-minute flurry, Republicans abruptly pulled their backing with no explanation and ultimately killed the measure, leaving its fate unclear, many of its champions livid and some of its newfound opponents professing ignorance about what had happened.

Asked what made him vote against a measure that he had co-sponsored, Representative Vern Buchanan, Republican of Florida, was brief and blunt: “I don’t know,” he said.

The real answer is as much an allegory about the state of House Republicans in 2022 as it is about a federal building in Florida. With little notice and nothing more than a 23-year-old news clipping, a right-wing, first-term congressman mounted an 11th-hour effort on the House floor to persuade his colleagues that Judge Hatchett, a trailblazing judge who broke barriers as the first Black State Supreme Court justice south of the Mason-Dixon line, was undeserving of being honored.

The objector was Representative Andrew Clyde of Georgia. Shortly before the House vote, he began circulating an Associated Press article from 1999 about an appeals court decision that Judge Hatchett wrote that year that struck down a public school policy allowing student-approved prayers at graduation ceremonies in Florida. The decision, which overruled a lower court, held that the policy violated constitutional protections of freedom of religion.

“He voted against student-led school prayer in Duval County in 1999,” Mr. Clyde, a deacon at his Baptist church in Bogart, Ga., said in an interview. “I don’t agree with that. That’s it. I just let the Republicans know that information on the House floor. I have no idea if they knew that or not.”

Since being sworn in last year, Mr. Clyde has drawn attention for comparing the deadly Capitol attack to a “normal tourist visit” and voting against a resolution to give the Congressional Gold Medal to police officers who responded that day. He also opposed the Emmett Till Anti-Lynching Act, which made lynching a federal hate crime and explicitly outlawed an act that was symbolic of the country’s history of racial violence. Mr. Clyde also voted against recognizing Juneteenth as a federal holiday.

The naming of federal buildings is among the more mundane tasks that Congress undertakes, and it is usually a consensus matter. In the Senate, it is often accomplished without debate or even a recorded vote, which is how that chamber passed the measure to honor Judge Hatchett in December. In the House, it is typically considered under a fast-track process reserved for uncontroversial matters that limits debate and requires a two-thirds majority for passage.

But Mr. Clyde’s late objection turned the routine ritual into a conservative litmus test for Republicans, who quickly joined him in turning against Judge Hatchett.

The bill failed on a vote of 238 to 187, falling short of the two-thirds threshold, with 89 percent of Republicans opposed.

“I was appalled,” said Representative Kathy Castor, Democrat of Florida, who grew up hearing about Judge Hatchett from her father, a former county court judge. “I was looking around, saying, ‘What is happening?’”

A legal legend in his state, Justice Hatchett could not stay in the hotel where the Florida bar exam was being administered when he took it in 1959 because of Jim Crow laws segregating the South. When he was nominated by President Jimmy Carter to the United States Court of Appeals for the 11th Circuit, Judge Hatchett was the first Black man to serve on a circuit that covered the Deep South.

Senator Marco Rubio, Republican of Florida and one of the bill’s sponsors, said the judge, an Army veteran who died last year at 88, had “lived an inspiring life of service.”

Senator Rick Scott of Florida, a Republican who co-sponsored the measure, said in a statement after the Senate passed the bill in December that Judge Hatchett “broke barriers that have inspired countless others in the legal profession.”

But Mr. Clyde found the school prayer ruling disqualifying, and the vast majority of House Republicans — including many who had initially co-sponsored the legislation — were quick to join him.

“During the vote series, a colleague shared some of the judge’s rulings with me I had not previously read,” Representative Matt Gaetz, Republican of Florida, said in a statement. “This caused me to withdraw my support for the measure.”

Representative Gus Bilirakis, Republican of Florida, who was recuperating at home with broken ribs, voted by proxy against the bill.

“Upon learning of the controversial ruling, Congressman Bilirakis no longer wished to proceed with the building name change,” a spokeswoman said. She said he had signed on to the bill only as a “professional courtesy to the bill sponsor to allow for its consideration.” (The entire state delegation must sign off for a naming bill to be considered.)

Other supporters of the bill who ultimately voted against it said they were confused about what was happening on the House floor. Staff members for Representative Kat Cammack, Republican of Florida, were scrambling to figure out why the vote had started to go south, calling other offices to determine what was happening.

A spokesman for Mr. Buchanan, who initially did not provide a reason for his vote, clarified that the congressman had opposed the bill “because of the judge’s position against prayer at graduation ceremonies.”

Representative Kevin McCarthy, Republican of California and the minority leader, also voted “no.” He declined to comment on why he opposed the measure.

Mr. Clyde said a legislative aide had unearthed the 1999 ruling while vetting the courthouse naming bill, and he made sure to share it with his colleagues before the vote.

Livid as she watched the red lights signifying “no” fill the vote board on the wall of the House chamber, Ms. Castor said she approached one of her Republican colleagues on the floor, searching for answers.

“They didn’t articulate a reason for voting ‘no,’” she said. “It was knee-jerk, herd mentality.”

Some Democrats noted that in the decision in question, Judge Hatchett had followed the U.S. Supreme Court’s 1992 decision in Lee v. Weisman regarding student prayer in public schools.

They said they saw the episode as the latest example of extremism in the House Republican Conference, where members have weaponized cultural issues against Democrats and pushed back against efforts to grapple with the nation’s history of racism, such as the push to strip Confederate names from military bases.

“If the standard that we use is one ruling out of thousands, then what else could we conclude but that they are not willing to name a courthouse after a Black person,” said Representative Debbie Wasserman Schultz, Democrat of Florida. “It seems pretty suspect.”

Mr. Clyde insisted that race had nothing to do with his opposition to the measure. “We’re one race — the human race,” he said. “It has everything to do with the decision he made.”

Democrats said the fact that Mr. Clyde, one of the most junior Republicans in the House, was able to derail an uncontroversial bill that had already passed the Senate was the latest evidence that Mr. McCarthy could not control the most conservative and fringe elements of his conference.

“The inmates are running the asylum, and the minority leader is terrified to do anything but cast his lot with the most extreme and unhinged elements in his party,” said Drew Hammill, a deputy chief of staff to Speaker Nancy Pelosi.

A spokesman for Mr. McCarthy declined to comment.

Representative Al Lawson, Democrat of Florida, who sponsored a House version of the bill, said the last-minute Republican stampede against it during the final seconds of the vote was “abhorrent.”

Mr. Rubio has expressed optimism that the setback will be temporary and that Congress will find a way to name the courthouse after Judge Hatchett. House leaders are working on next steps to bring the legislation back to the floor, Mr. Hammill said.

Still, the setback has been unsettling for Judge Hatchett’s former colleagues, family members and supporters, who have called on the House to reconsider.

“What a black eye,” Ms. Castor said. “What a stain on these folks, who sponsored a bill and then flipped.”