* I began writing this post before the ABC interview with Gingrich's second wife was announced
I believe any of the remaining candidates are electable, even Ron Paul. Even as hard as Obama will fight against any of them, and with as much money as he has, any of them could replace him as president because his presidential record is so bad. He was NOT vetted before nomination or election. And while the media isn't going to press that issue and will do everything to assist Obama in smearing the GOP nominee, there are other sources of information and opportunities to learn about Obama's failures in office than the traditional media.
That said, one candidate is more vulnerable to personal attacks than the rest. That person is Newt Gingrich. Obama got himself into politics in the first place by smearing his divorced opponents at the local level for Illinois Senate and then the state level for the US Senate. Newt is more than divorced. He is divorced twice, and for infidelity! He would be vulnerable, very vulnerable indeed. Sure, he's conservative, but he's got a spotty record when it comes to either consistency or constancy.