The Supreme Court is hearing two landmark cases on same-sex marriage this week, but "one thing is already clear: The political debate over gay marriage is over," says Chris Cillizza at The Washington Post. Politicians and their strategists can read polls, and the uptick in support for legalizing same-sex marriage is unambiguous. (See The Week's timeline on America's gay-marriage evolution since 1971 here.)

It's pretty clear that welcoming gay marriage will be a part of the Democratic Party platform for the foreseeable future. Potential 2016 presidential front-runner Hillary Clinton announced her support in a video last week. Red state Sen. Claire McCaskill (D-Mo.) casually declared her approval of same-sex marriage on Sunday, via her Tumblr page, citing St. Paul's letter to the Corinthians. Now, the real question is whether gay marriage will become an issue that divides roughly along partisan lines, like abortion rights, or whether Republicans will join Democrats, marking a more national evolution on the issue.

Some Republican officials — and fundraisers — see Sen. Rob Portman (R-Ohio) coming out for gay marriage earlier this month as a bellwether for the party. "There's no putting this genie back in the bottle," Florida-based GOP strategist Ana Navarro told CNN on Sunday. Also on Sunday, Karl Rove told ABC News that he could imagine one of the 2016 candidates for president fully supporting gay marriage (though not necessarily "THE Republican presidential candidate or the GOP presidential nominee," he later clarified in a statement). "That's not the same as saying the GOP nominee will definitely support gay marriage," says ABC News' Rick Klein.

But the fact that this would be a plausible position inside the Republican Party in time for 2016 is a stunning turnabout. Barely eight years ago, Rove engineered a re-election campaign that took advantage of a wave of state efforts to move in the other direction, by banning gay marriage. [ABC News]

The Supreme Court showdown, especially, "has exposed fissures within the Republican ranks" on gay marriage, says Seth McLaughlin at The Washington Times. Already, potential presidential contenders like Sens. Rand Paul (R-Ky.) and Marco Rubio (R-Fla.) are backing the rights of individual states to determine who can legally tie the knot, putting them at odds "with the more socially conservative elements of their party, including potential rivals for the GOP nomination, and the party's 2012 platform, which endorsed a constitutional amendment banning gay marriage."

The Week's Marc Ambinder, for one, is (cautiously) skeptical that the GOP and its standard-bearers can afford to embrace gay marriage:

Nearly 8 in 10 Americans under 30 support gay marriage. Nearly every Republican I talk to supports it, too, which makes it hard for me to conceive of a world where the GOPers who are potentially available to vote in the party's primaries wouldn't support it. But they do not. And as I've written, I don't think they will for a while. I do not think that the party is structured to reward a modernizing socially moderate candidate.... The traditionalists still vote in the primaries and caucuses. Tea Partiers overlap more with libertarians on some issues than your generic non–Tea Party conservative might, but they're still social conservatives. [The Week]

And the socially conservative wing of the GOP is, of course, still very much opposed to gay marriage. "I would just say to Republicans generally who want to be president that we are living in an America where liberal courts are day-by-day ripping out of the public square our Judeo-Christian worldview," warns prominent evangelical Christian leader Gary Bauer. When Fox News Sunday host Chris Wallace brought up recent polling that shows the growing support for same-sex marriage, even among younger evangelicals, Bauer stuck to his guns (watch below):

Frankly, the argument that the public is overwhelmingly in favor of same-sex marriage, Chris, is ludicrous. Thirty-three states have voted to keep marriage the union of one man and one woman.... I'm not worried about it because the polls are skewed, Chris. Just this past November, four states, very liberal states, voted on this issue. And my side lost all four of those votes. But my side had 45, 46 percent of the vote in all four of those liberal states. In fact, those marriage amendments that I supported, that would keep marriage of a man and a woman, outran Mitt Romney in those four liberal states by an average of five points. [Fox News]

And yet, notes The Washington Post's Cillizza, a recent poll of Ohioans found that 54 percent want to repeal the constitutional amendment banning gay marriage that 62 percent of Buckeye State voters approved just nine years ago. And as younger voters replace older generations, numbers like that will likely grow more pronounced. "All of the above is not to say that the Republican Party will shift its broadly held opposition to gay marriage — at least any time soon," Cillizza adds, citing Ohioan John Boehner (R), the House speaker, saying last Sunday, "I can't imagine that position would ever change."

But, the trajectory of the data suggests that ambitious Republicans who want to win statewide in swing states or get elected president in 2016 and beyond simply won't proactively talk about the issue. Outside of Republican primary fights, gay marriage will disappear from the national political dialogue as an issue. [Washington Post]

Watch Bauer: