Here is a twist on this conversation. Since the election is over.. here is some conversation room..
Who would the characters on Buffy vote for? It might be all one side, I dunno..
Just at a guess I would say that Willow and Tara would be staunch Democrats, given that party's support of gay rights.
If anyone in the group was going to be a Republican, it would be Xander, if for no other reason, because Anya would insist on it in favor of the Republicans' stand on lowering taxes. (Are we assuming that Anya will have the proper credentials to become a registered voter? If so, she would obviously be a Republican)
And then we have Buffy. I know that Sarah is a staunch Republican, and on the NRA's support list for opposing gun control, so I suppose that her character would be, also.
Giles is a total mystery, but at a wild guess, I'll say Democrat, as would be Gunn.
Given Wes' fondness for firearms, he would HAVE to be a Republican.
Cordy might pretend to be a Democrat as a hold over from her acting days, but she's probably a Republican at heart.
Angel, we know, is a Charlton Heston fan, so just on a whim, I'll say that he's not only a rock solid Republican, but also a long standing member of the National Rifle Association, with a poster of Heston with his flintlock rifle raised high shouting "FROM MY COLD DEAD HANDS!" displayed somewhere prominently in his room.
And that leaves us with Spike. He had a shotgun in his crypt, and liked the fake handgun the Xander gave him when he dressed up like a member of the Initiative, so he's probably a Republican as well, but goes to great lengths to conceal the fact because he doesn't want anyone to know that he has anything in common with Angel.