Ezra Klein asks:

Perhaps more Republicans would have run if Obama had looked this weak eight months ago. But Obama’s numbers have been sinking for awhile now. Entering the race late makes it tougher to win, but it doesn’t make it impossible. And it’s hard to believe that Romney had such an imposing head start that he scared off a larger field. His dominance has come as a surprise to everyone. So help me out. What’s the answer here?

Christie isn't ready. Daniels didn't have the charisma or balls. Jeb's last name is Bush. The new crop of governors – Rubio, Scott, Walker – is too green. Barbour is too Southern. Palin couldn't handle more scrutiny of her actual life. Sometimes, no grand theory is needed. Events and timing matter. It reminds me of the Dems in 1991. But they had a Clinton in the pack of cards. A rogue card, but better than any that the GOP now has.