One place the issue hasn't changed much: The GOP caucus on Capitol Hill.
By and large, Republican lawmakers in Congress have maintained their opposition to same-sex marriage, although they are trying to talk about it in ways that are more in tune with the change in public opinion.
“I do believe that marriage is between a man and a woman,” Sen. Dean Heller, R-Nev., told the Washington Examiner. “But that doesn’t mean there aren’t different variations of that, and I’ll continue to follow the issue.”
Like other GOP lawmakers, Heller must walk a careful line of holding onto the support of a base of conservative voters without offending the broader electorate. In Nevada, where gay marriage is not legal, the views have shifted enough that the state Republican Party stripped the definition of marriage from the party platform in April.
“That goes to show you that, yeah, things are slowly changing,” Heller said.
But Heller is not ready to back gay marriage, and neither is Sen. Pat Toomey, R-Pa., whose own Republican governor has refused to challenge a federal court ruling in May striking down the swing state's ban on same-sex marriage.
“My views are the same as they have been,” Toomey told the Examiner, declining to comment further.
On June 26, 2013, the Supreme Court overturned parts of a federal ban on recognizing gay marriage while stopping short of finding a constitutional right to gay marriage. Since then, gay marriage backers have won a string of 22 court cases which followed the Supreme Court's logic to that conclusion. On Wednesday, federal judges overturned gay marriage bans in Utah and Indiana.
At the same time, the public has grown more supportive.
Most Senate Republicans still oppose recognition of same-sex marriages, though moderates are beginning to change their view.
On Wednesday, Sen. Susan Collins, of Maine, who is one of the most moderate Republicans in the Senate, announced her support for gay marriage.
“A number of states, including my home state of Maine, have now legalized same-sex marriage, and I agree with that decision," Collins said.
Kirk, who announced his support in April 2013 -- seven months before the Illinois state legislature passed a law recognizing gay marriage -- said the issue has become “the litmus test for whether you are moderate on social issues.”
But for many, there's no reason to talk about the issue, which is currently being fought mostly in statehouses and courtrooms.
Sen. Marco Rubio, R-Fla., said many in the Republican Party are simply backing the rights of their states to decide whether to legalize gay marriage.
“Marriage has always been something that has been regulated by the states,” Rubio told the Examiner. “Some Republicans support those changes in state laws [supporting gay marriage], and they certainly have the right to define marriage differently. That’s reflective of how public opinion in America is moving.”
Other Republicans have taken baby steps in the direction of accepting gay marriage.
Sen. Ron Johnson, R-Wis., personally opposes same-sex marriage, but he recently told CNBC that if the voters in his state decide to support gay marriage, “I'm not going to oppose it.”
A federal judge struck down Wisconsin's ban on June 6, although the state is not issuing same-sex marriage licenses while the state attorney general appeals the ruling.
In the House, only four of 233 Republicans favor of gay marriage. But that could shift slightly next year if three gay GOP candidates are elected.
Candidates Dan Innis and and Richard Tisei, who are running in competitive races in New Hampshire's 1st Congressional District and Massachusetts' 6th District, respectively, are both gay and married.
In California, House GOP candidate Carl DeMaio has walked hand-in-hand with his male partner in parades and campaign stops in his bid to win state's 52nd District seat.
Of the three candidates, Tisei and DeMaio are leading their Democratic challengers in the polls by significant margins and stand the best chance of winning in November. They would become the first openly gay House Republicans since Rep. Jim Kolbe of Arizona retired in 2006.
Still, two gay colleagues aren’t likely to sway the thinking of the mostly conservative House rank and file, House Republicans said.
Rep. John Fleming, R-La., who supports the gay marriage ban in his state, said despite poll numbers and court decisions, the House GOP is not ready to abandon its support for the traditional family, made up of a mother and a father.
“On the one hand, there is more acceptance of gay lifestyle, but on the other hand that doesn’t necessarily mean that it is a change in the attitudes and ideas about the traditional family,” Fleming said. “It’s very nuanced. But, we want to fairly represent the people that we serve.”