WASHINGTON (AP) — When asked if he'd support legislation to protect same-sex marriage, one conservative Republican senator was almost nonchalant.

"I see no reason to oppose it," Ron Johnson of Wisconsin told reporters, bringing Democrats one vote closer to an unexpected victory as they move to safeguard same-sex marriage and other rights after the Supreme Court overturned Roe v. Wade, which legalized abortion nationwide.

Johnson's answer, which came after 47 Republicans voted for the bill in the House last week, was reflective of a stark shift in GOP positioning after decades of fighting same-sex marriage. Ten years ago, most Republicans proudly espoused that marriage could only be between a man and a woman. Now, a federal law protecting same-sex marriage is within reach in an election year, with some Republican backing.

The signal of possible support from Johnson — arguably the most vulnerable Republican senator up for reelection this year — comes as Wisconsin's other senator, Tammy Baldwin, is the lead Democrat charged with persuading the necessary 10 Republicans to vote for the bill. Baldwin, who is the first openly gay senator and has been working on gay rights issues since she first entered state politics in 1986, says the "world has changed," especially since the Supreme Court's 2015 Obergefell v. Hodges decision upholding gay marriage.

A Gallup poll conducted in May showed broad support for same-sex marriage, with 71% of U.S. adults saying they think such unions should be recognized by law, including 55% of Republicans. Polling in Wisconsin mirrors that national survey, with 54% of Republicans in the state saying that they favor same-sex marriage in a Marquette Law School poll from April. In May 2014, the state poll found support from only 23% of Republicans.

"People began to see that the sky has not fallen," Baldwin said in an interview, and that the 2015 decision gave legal protections to families who did not previously have them. She says every member of Congress now has friends, family or staff who are openly gay.

"That probably has the biggest impact on where people land," she said. "This is a vote of conscience."

The bill pending in the Senate would repeal the Clinton-era Defense of Marriage Act that allowed states to refuse to recognize same-sex marriages and instead require states to recognize all marriages that were legal where they were performed. The new Respect for Marriage Act would also protect interracial marriages by requiring states to recognize legal marriages regardless of "sex, race, ethnicity, or national origin."

A vote could come as soon as next week, but it will more likely be in September when Congress returns from the August recess.

Republican Sens. Rob Portman of Ohio, Susan Collins of Maine and Thom Tillis of North Carolina have also said they will vote for the legislation; Alaska Sen. Lisa Murkowski has also supported same-sex marriage in the past. Several other Republicans have said they are undecided, including Utah Sen. Mitt Romney, Missouri Sen. Roy Blunt, Iowa Sen. Joni Ernst and Indiana Sen. Mike Braun.

Notably silent is Senate Republican leader Mitch McConnell, who has declined to comment until Senate Majority Leader Chuck Schumer holds a vote.

Baldwin and other advocates say more GOP senators are quietly contemplating the bill. Democrats need 10 Republican votes to overcome a filibuster and get a bill through the 50-50 Senate.

A range of Republicans voted for the bill in the House, including New York Rep. Elise Stefanik, the No. 3 House Republican; Pennsylvania Rep. Scott Perry, the chair of the conservative House Freedom Caucus; and all four Republican members of Utah's congressional delegation.

Still, the majority of House Republicans voted against it, and a similar dynamic is expected in the Senate.

Republicans opposing the bill give a variety of reasons, with most arguing that the Supreme Court is unlikely to overturn Obergefell and that Senate Democrats are playing politics by putting the bill on the floor. Democrats point to Justice Clarence Thomas ' concurring opinion to the June ruling overturning Roe in which he said that high court rulings protecting same-sex marriage and the right for couples to use contraception should also be reconsidered.

Asked about their opposition, many Republicans have focused on the process rather than the substance.

Florida Sen. Marco Rubio, who is up for reelection this year, told CNN last week that he thinks the bill is a "stupid waste of time." He said later that he believes "there is zero chance, below zero chance, that the Supreme Court or anyone is going to outlaw gay marriage in this country."

Even Johnson blamed Democrats as he said he was unlikely to oppose it, arguing that it was settled law and the vote is unnecessary. He said he still believes that marriage should be between a man and a woman. But "society has pretty well accepted it and moved on," he said.

Other Republicans have made similar arguments, shifting from the more ideologically rigid statements of years past.

Texas Sen. Ted Cruz, who will vote against the bill, said he recognizes that "reasonable people can disagree" with him that marriage should be between a man and a woman, "and there is room for a diversity of views on that question."

North Dakota Sen. Kevin Cramer says he will vote against it "unless I can be compelled somehow." He says he believes because of his evangelical Christian faith that marriage is between a man and a woman, but "it's not like I feel super strongly about it, either."

Cramer said he thinks the Senate will get the 60 votes needed to pass the bill. "It's more that people are ambivalent about it," he said.

Portman, who is pushing to get more votes from his party, notes that public opinion has changed substantially over the years. He has supported same-sex marriage since 2013, when he announced that one of his sons is gay and that he believes people should be respected for who they are.

He faced criticism from some fellow Republicans at the time, but he says people now come up to him frequently to thank him for his support.

It's not just Republicans who have evolved on the issue. Former President Barack Obama didn't publicly support same-sex marriage until 2012, pushed in part by then-Vice President Joe Biden, who had come out in support a few days earlier. When the Defense of Marriage Act passed the Senate in 1996, only 14 Democrats opposed it.

David Stacy, a lead lobbyist for the Human Rights Campaign, says advocates for same-sex marriage faced many setbacks in the early 2000s, including state ballot measures to ban gay marriages. But he says he believes Republicans created a backlash of sorts by trying to use the issue against Democrats.

While the advocates lost many of those fights, "we were educating the public and moving public opinion," Stacy says.

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Associated Press writers Hannah Fingerhut in Washington and Scott Bauer in Madison, Wis., contributed to this report.