If by some miracle a pro-path to citizenship Bush made it through the primaries and picked the pro gay marriage Portman, then yes that wold be a strong GE ticket. Clinton could pick one of the VA Senators and then you could have a weird situation where FL,VA and OH (where most of the money in 2012 was spent) all moved out of the tipping point state category and the fight would be for CO, IA, NH, NV, WI and maybe NC (depending on how AAs trend).
• If Dems looked likely to take back Senate and House, I'd vote Bush. • If GOP looked likely to hold both Senate and House, I'd vote Clinton.
• If Dems looked likely to take back Senate and GOP looked likely to hold the House, I'm not sure. I'd be "Leans Clinton", but Bush and Paul are currently the only two seriously considered contenders for whom I could be persuaded to vote.