Of the choices given (and, let's face it, everyone hates the "other" vote) I chose Edwards because he's a southern Democrat and he is quite likable. And Bayh just sucks.
Bayh would be a centrists dream given the opportunity to run. I can't see him having a high negativity rating among the electorate as a whole. He's moderate enough (pretty close to the ideological centre) and would be a far from polarising candidate
Bayh's base in 2004 (according to exit polls in Indiana) was as follows:
Democratic 29.44 + Independent 16.06 + Republican 16.1 = 61.6%
Liberal 12.18 + Moderate 33.11 + Conservative 15.91 = 61.2%
Dave