I'm voting for Hillary, but for the rest...
Sarah Palin... Not experienced or sharp enough. Doesn't know world leaders or geography. Thinks "What books or newspapers do you read" is a trick question setup by the 'Liberal media'. Her family is weird, she'd never get far. And she makes too much money at speaking engagements to give that up.
Michelle Bachman... To weird, extremely creepy husband. America and Republicans would never warm up to him.
Rand Paul... I dunno
Mitt Romney... He got creampied heavily by Obama. He wouldn't win against Hillary.
Jeb Bush... He has the best shot at winning, but all dems have to do is replay the Iraq war over and over, created by the Bush's, and that will be a big problem for them.
Plus America is tired of Bush presidents.
Chris Christie... Morbidly obese and rude. No one wants to look at an obese president, and NJ has terrible taxes and hurricane Sandy cleanup was a disaster.
Jim DeMint: Who?
Lindsey Graham... Not good looking enough and doesn't give an inspiring speech. And put "is Lindsey Graham" into Google and see the rest :D
Jon Huntsman... Who?
Bobby Jindal... lol
Bob McDonnel... who?
T-Paw Tim Pawlenty... who?
Rick Perry (Really!)... LOL
Marco Rubio... meh. Doesn't look presidential, but I guess it could happen since there are so many Mexicans here now, they could push him over. But doubt it.
Paul Ryan: lol
I think a Jeb Bush/Marco Rubio ticket would have a serious chance of winning.
btw I would LOVE a President Bloomberg

I Love no bullshit business men as leaders