Nate Silver has some sharp analysis of the race going forward:

Whatever your perspective on how likely Mitt Romney was to lose the Republican nomination race prior to Tuesday evening, it should be acknowledged that he had about the worst results conceivable.

In Minnesota, a state which Mr. Romney carried easily in 2008, he has so far failed to win a single county - and got just 17 percent of the vote. That put him 27 points behind Rick Santorum, and 10 points behind Ron Paul, who finished in second.

Missouri is a less important result since its beauty contest primary did not count for delegate selection and since turnout was understandably low there. But Mr. Romney lost all 114 counties in Missouri - and the state as a whole by 30 points, far more than polls projected.

Then there was Colorado, a state that has reasonably similar demographics to Nevada, which Mr. Romney carried easily on Saturday. Colorado has somewhat fewer Mormon voters than Nevada, which hurts Mr. Romney - but it has somewhat more wealthy ones, which favors him. The betting market Intrade gave Mr. Romney about a 97 percent chance of winning Colorado entering the evening. But he lost the state by 5 points to Mr. Santorum.

What's more, the victor in all three states was Mr. Santorum, who is probably much more dangerous to Mr. Romney than Newt Gingrich. Mr. Gingrich had an awful evening, finishing a distant third in Colorado and last in Minnesota. But that may only work against Mr. Romney in the end.

Silver believes that Romney may be in trouble largely because of his continued unacceptability to the base. But other Republican voters are also disgusted with their choices and appear to be taking it out on Romney. They don't want a coronation. They want a race that will define a clear winner and strongly represent the party in the general election.

Romney has disappointed in that regard. And the voters are telling him so. He may still end up the nominee, but he better start showing some fight or Santorum or Gingrich are going to pass him up.