I'm not so certain about that. To be sure, many conservatives (including many FRiends here) would sit out the election if Romney is the Republican nominee, but many independents who will not vote for Perry (or Bachmann or Palin) would vote for Romney over Obama. It is an unpleasant fact that independents are the key to the election, as always. Wishing it were otherwise is fruitless. We have to find the most conservative candidate who is electable, and that means the most conservative candidate who can pull the most independents away from Obama. Right now, I don't know who, among the announced candidates, that person is.
Then consider how many sitters would get off their butt for Cain/Palin, and still take 6-7 percent of the indies who are in fact totally rejecting omaba.
Either way close call, would depend on how hard hitting and convincing the campaign was. Lord knows there is sufficient material in his record to sink the man. The ability to get that to the eyes and ears of the average voter is the problem.