WASHINGTON — It began for Democrats as a messaging vote, an election-year political maneuver to show voters that they were doing everything possible to protect marriage equality in the face of new threats from a conservative Supreme Court — and a move to force Republicans to put their opposition on the record.
But when the House called its vote this week on the Respect for Marriage Act, which would codify federal protections for same-sex couples that were put in place in a 2015 ruling, 47 Republicans voted “yes.” That raised the possibility that there could be a narrow bipartisan path for the legislation to move ahead in the Senate and make its way to President Biden’s desk to be signed into law.
Senator Mitch McConnell, Republican of Kentucky and the minority leader, who has positioned himself as an obstacle to most of the Democrats’ agenda, declined to reveal a stance on the bill. And on Wednesday, four Republican senators — Susan Collins of Maine, Rob Portman of Ohio, Lisa Murkowski of Alaska and Thom Tillis of North Carolina — said they supported it.
In the space of 24 hours, Senator Chuck Schumer of New York, the majority leader, shifted from declining to commit to a vote on the measure on Tuesday to saying that he intended to bring it to the floor. Mr. Schumer also said he was working to get the requisite 10 Senate Republicans on board to ensure that it could move a bill past a filibuster.
“This legislation is so important, I was really impressed by how much bipartisan support it got in the House,” he said on Wednesday.
There was no guarantee that Republicans would allow the measure to move forward in the Senate. But the developments made it clear that a bill that was supposed to be dead on arrival was now an open question — and that the evenly divided Senate was likely to weigh in, months before the midterm elections, on whether same-sex couples should have the right to wed.
Senator Tammy Baldwin, a Wisconsin Democrat who in 2012 became the first openly gay woman elected to the Senate, was speaking with Republicans to gauge whether there would be enough support for the bill to pass, Mr. Schumer said. He also discussed it with Ms. Collins, a co-sponsor, on Wednesday, an aide said.
The push in Congress to pass legislation codifying marriage protections came after Justice Clarence Thomas suggested last month in an opinion overturning abortion rights that the court “should reconsider” past rulings that established marriage equality and access to contraception.
With their control of Congress hanging in the balance in November’s elections, Democrats are seeking to draw clear distinctions with Republicans on issues that have broad resonance for the public. The overturning of Roe v. Wade last month dramatized the stakes and drove home the prospect that the court could strip away more protections, with no recourse in Congress should Republicans win the majority.
The demise of Roe also prompted outrage among progressives who have harshly criticized Democratic leaders for having failed to safeguard abortion rights when they had the chance and being slow to respond to a Supreme Court ruling that had been expected for months.
But on the issue of same-sex marriage, as opposed to abortion, Republicans are deeply divided. Many conservative lawmakers have switched their positions over the past decade, as the country overall has come to accept same-sex marriage as a settled matter.
About 71 percent of Americans, including most Republicans, support it, according to a recent Gallup poll, up from just 27 percent in 1996.
Mr. Portman, who is co-sponsoring the legislation, flipped his position in 2013 after his son came out as gay. In the House, Representative Liz Cheney, Republican of Wyoming, admitted last year that “I was wrong” to oppose same-sex marriage, reversing a longstanding position that had put her at odds with her family, including her sister, who is gay and married.
Still, while the proportion of House Republicans who supported the marriage equality legislation this week was higher than expected, it was less than one-quarter of the conference. Most Republican senators were similarly unenthusiastic about the bill.
On Wednesday, many of them were either dismissive or noncommittal about how they would vote, with some accusing Democrats of trying to distract from inflation and other pressing national issues. Others contended that the vote was unimportant or unnecessary because same-sex marriage protections were not under genuine threat.
Senator John Thune, Republican of South Dakota, told CNN that he respected the 2015 Supreme Court decision in Obergefell v. Hodges that legalized same-sex marriage nationwide, but that overturning it was not “an issue right now that anybody’s talking about.”
Justice Thomas did talk about it in his recent opinion, and Justice Samuel A. Alito Jr. has also suggested before that Obergefell should be revisited, arguing that it invented a right with no basis in the text of the Constitution.
Senator Tommy Tuberville, Republican of Alabama, said that he saw no need to pass legislation to protect gay marriage, but that he supported it in practice.
“Yeah, if that’s what you want to do, fine,” he told reporters.
Senator Marco Rubio, Republican of Florida, said he would oppose the bill and told CNN that it was a “stupid waste of time.”
He added, “I know plenty of gay people in Florida that are pissed off about gas prices.”
Senator Mitt Romney, Republican of Utah, said he was not focused on the bill because same-sex marriage was still protected by Obergefell.
“I don’t think we need to lose sleep over it unless there were a development that suggested the law was going to be changed,” Mr. Romney said.
Senate Democratic aides said it was encouraging that House Republican leaders did not whip “no” votes on the bill on Tuesday, indicating that the party was divided on the issue of same-sex marriage. In fact, the party’s leaders split on the bill.
The top two Republicans, Representatives Kevin McCarthy of California and Steve Scalise of Louisiana, voted no. But the No. 3 Republican, Representative Elise Stefanik of New York, and Representative Tom Emmer of Minnesota, the G.O.P. campaign committee chairman, were in favor.
Still, it was not clear where six more Republican votes in favor of the legislation could be found in the Senate.
Mr. McConnell, who has been explicit in the past about the party’s need to appeal to suburban voters, was not tipping his hand.
“I’m going to delay announcing anything on that issue until we see what the majority leader wants to put on the floor,” he told reporters on Tuesday.
The bill, which codifies the right to marriage regardless of gender or race, also protects interracial marriage. Mr. McConnell’s wife, Elaine Chao, was born in Taiwan.
Democrats saw no political downside in waiting to see if they could muster enough votes for passage. Until then, they noted privately that they were forcing Republicans to squirm as reporters peppered them with questions about an issue that most of the rest of the country had long since decided was uncontroversial.
On Wednesday, as Republican senators demurred on their positions, the Senate Majority PAC, which raises money to protect and expand the Democratic majority in the Senate, noted that many Republican senators “refuse to say whether they would protect basic human rights” and that “a Republican Senate majority would be dangerous for our country.”