Gallup released a poll today finding that half of Americans support gay marriage. The numbers are 50-48 — the second time Gallup has found that support for marriage equality has hit the 50 percent mark.

The more interesting finds may be in the ideological and demographic breakdowns. Gallup sends over some more numbers, and it turns out that self-described moderates support it by a larger margin, 58-38. Unsurprisingly, an overwhelmingly majority of liberals, 83 percent, back it. This has left conservatives all alone on this one: Only 26 percent of them support it, versus 72 percent who are opposed.

Gallup also finds that independents favor marriage equality by 57-40. Here, too, Republicans are all alone: Only 22 percent back it, while 74 percent are opposed.

It’s been widely reported that Obama fears coming out for marriage equality because it could alienate culturally conservative Dems and independents in swing states. Perhaps, but sizable majorities of moderates and independents support it, making Obama’s stance all the more mystifying (though no one believes he actually opposes it).

That said, there is one other interesting data point: Gallup tells me that non-college voters oppose gay marriage by 56-43. This appears to include African Americans, but it also suggests blue collar whites — a demographic Obama has alienated and needs to win back — risk getting put off over the issue. (Incidentally, as Molly Ball points out, non-whites oppose gay marriage in almost exactly the same proportions as the rest of Americans do.)

Ultimately, the broader trends show that the American public is slowly coming around to the inevitable. Moderates and independents are now siding in big numbers with liberals and Democrats. The last holdouts are conservatives and Repubicans, whose isolation on the issue remains striking: They continue to oppose gay marriage in huge numbers. No wonder Mitt Romney is touting it as a positive that unlike Obama, he will never evolve and intends to rigidly hold out against full equality for gay and lesbian Americans for as long as he lives.