Depends if he can get Romney to fold like Bush, or if Romney stands up to him like he stood against the rest of the anti-Romneys.
That would be four year early. The political mood was different. I don't see him winning the nomination. If he does, he loses by a landslide, like he will this fall. Obama would have a Democratic House 2013 - 2015.
I assume the idea is that Trump alienates enough Republicans into not voting/terrifies enough Democrats into voting that the down-ballot effects support the Democrats more. I'm not sure if it would be enough; the House is sufficiently gerrymandered that it would take a fairly phenomenal swing in population to allow the Democrats to come back (they won a majority of the House votes as it was, they were just not well distributed). If the Democrats did take the House, however, another 2 years of effective governance (rather than gridlock) would be huge; they would still collapse in 2014, however.Why would Obama have a democratic house?
however, another 2 years of effective governance (rather than gridlock) would be huge; they would still collapse in 2014, however.