Who will be the next currently-serving Senator to endorse same-sex marriage?

[tpfkaw]

I'll say Pryor, assuming he isn't reelected.

[Vega]

I'm going to be bold and say John McCain.

[Atlas Has Shrugged]

Certainly not Ayotte, who resigned as AG when same-sex marriage was passed.

[IceSpear]

Heller. He's going to need a lot of moderate cred if he wants to get re-elected, and by 2018 I doubt there will be any danger of getting primaried for it.

[Chance92]

Heller. He's already moderate enough, and I can only see him becoming more of one.

[ElectionsGuy]

I'm going to say Manchin. He's the only Democrat that won't lose that is anti-gay marriage. Eventually approval will get to the low 60's and he'll realize its the smart move to change his position.

[HagridOfTheDeep]

I hope John McCain does change is mind. It would send a big signal to the party establishment and possibly help get the ball rolling.

[Grumpier Than Thou]

Lindsey Graham, after he comes out.

[Mr. Smith]

McCain, Graham is in the armored closet, Heller being a Mormon will probably dodge the question until Mike Lee or Orrin Hatch force his hand (yes Reid and the Udalls are Mormons too but they are outliers in a religion still having issues with even acceptance), and Manchin will probably get away for awhile too (as ElectionsGuy already said).

But McCain is still fairly moderate, and he'll probably need to switch sooner than the others for 2016.

[Rockefeller GOP]

Lindsey Graham, after he comes out.

Wow.

My answer is Heller or McCain.

[TDAS04]

Heller or Flake.