When you are done trashing romney and obama wins a second term, where are you going to go?
Second: Romney is the antithesis of the Tea Party movement. He was selected by the GOP-E as their boy to smack down the grass roots movement. When you support Romney you support the GOP-E in minimizing the impact of the real conservatives.
Third: a Romney win will move the Entire GOP leftward. Right now we have the far left Democrats and the somewhat left GOP. After a Romney win, especially if its a landslide, We will have both parties with a far left culture in place and the GOP Congress will happily (as they have done in the past) go along with every big government, liberty reducing, crony capitalist idea Romney comes up with. There will be no effective resistance. A leftist Romney with a mandate will b a terrible thing.