"Electability exists along a spectrum, rather than in absolutes. Mr. Romney could defeat Barack Obama under a wider variety of circumstances than, for instance, Christine O’Donnell. But if the United States were suffering from Zimbabwe-style hyperinflation in which all liquid wealth in the country was destroyed every 24 hours, I would start to like Ms. O’Donnell’s chances against Mr. Obama, too."
I think this is absolutely right. The economic and geopolitical conditions next year will play a big role in determining who wins the election. The identity of the Republican nominee will only matter at the margins, after those conditions are taken into account.