I don't think there are many openly LGB candidates who would qualify to be VP. Baldwin supported the TPP, so that would be a turn-off to progressives, a group that Clinton is already having some issues wooing. Jared Polis and Annise Parker don't have any name recognition that would boost Clinton's support. I have never been a fan of politicians choosing running mates based on their membership in a minority demographic (this is something the Republicans will almost certainly do next year: Fiorina's a woman, Rubio and Cruz are Latino, Carson is black, Jindal is Indian), but I think a strong progressive VP nominee (assuming Clinton doesn't select Sanders or O'Malley), who just so happens to be in a minority group, would be Keith Ellison of Minnesota; he is a Muslim and he is as progressive as Sanders, O'Malley, Elizabeth Warren, Sherrod Brown, Alan Grayson, etc.
Don't forget, Sanders himself is a minority, since he's Jewish. It doesn't have much bearing on his candidacy, but if he were a VP nominee, he would be the first Jewish one.
