Republicans don't get any more mainstream than Ohio Senator Rob Portman. He's so Republican, he was very nearly Mitt Romney's choice for vice president last year, until Romney decided he had to make a big splash and went for Paul Ryan instead. And now, Portman has announced that he's in favor of gay marriage:

Sen. Rob Portman has renounced his opposition to gay marriage, telling reporters from Ohio newspapers yesterday that he changed his position after his son Will told him and his wife, Jane, that he is gay.

Portman, an Ohio Republican, made the stunning revelation just a week before the U.S. Supreme Court hears oral arguments on a 1996 federal law asserting that gay marriage is not legal, a measure that Portman co-sponsored as a member of the U.S. House.

Portman couldn't do the full monty, though. He says gay marriage should still be a state-by-state issue. Still, this is huge news. Portman is as Republican as they come; his name has even come up a few times as a 2016 presidential contender. It'll be interesting to see how Republicans treat this news tomorrow at CPAC now that boring, reliable ol' Portman has backed off the bigot parade.