If Romney had not run, who would have won the Republican nomination?

[Mr. Morden]

Barbour had some serious pardon problems even before the end of his term:

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I don't think Huckabee was going to run anyway.  Romney wasn't the reason why Huck chose not to run.  I don't think Barbour, Daniels, Huckabee, or Palin would have run even with no Romney.  Jindal, Pence, and Ryan probably wouldn't have run either, but it's less certain.  Thune may well have run if no Romney.  Jeb Bush and Chris Christie *might* have done it.  Certainly, there would have been a bigger draft effort for one or the other of them, and remember that Christie very nearly changed his mind at the last minute and decided to run, even after all his denials.

If none of the aforementioned names had run, then I don't know.  Maybe Pawlenty?

[Mr. Morden]

Romney definitely didn't scare anyone out of the race. The people who didn't run, didn't want Romney as the nominee and STILL don't.

I don't think that's exactly right.  Without Romney, there would have been a gaping hole in the race where there should be an establishment party man who the big party donors can contribute their $ to (and who can then use that money to destroy his opponents, like Romney did).  If folks like Christie really came as close to running as they seemed to, then the lack of Romney might have been enough to tip the balance in favor of running.

[Mr. Morden]

Romney definitely didn't scare anyone out of the race. The people who didn't run, didn't want Romney as the nominee and STILL don't.

I don't think that's exactly right.  Without Romney, there would have been a gaping hole in the race where there should be an establishment party man who the big party donors can contribute their $ to (and who can then use that money to destroy his opponents, like Romney did).  If folks like Christie really came as close to running as they seemed to, then the lack of Romney might have been enough to tip the balance in favor of running.

The establishment candidates would have been Jon Huntsman and Tim Pawlenty.

Maybe.  I mean, sure, if no one else gets in the race, but they wouldn't have started out with the kind of lead in either NH or nationally that Romney started out with.  Even though early polls don't "matter", psychologically, the fact that no establishment candidate would have started out with an early polling lead (and wouldn't have been raising quite the same $ that Romney did IRL) would have made it look like the race was more open to a newcomer than it was IRL.  Maybe the only late entrant would have been Perry, as IRL, but who knows.  Butterflies can do strange things.