Ultimately, I wouldn't read too much into a Santorum victory in Colorado. We're talking about 66K people participating in the caucuses, or about 1.2% of Colorado's population. It's not really a reflection of "Colorado voters" as much as a reflection of a core group of motivated ideologues (as with any caucus regardless of party). And as we've already discussed here, the Tea Party was co-opted by the Religious Right not long after it became a political force. Pretty clear that the Christian Right were the most motivated in this election, and one county (El Paso) accounted for about 12% of the total turnout.
The bigger problem for the GOP is that the turnout for this year's caucuses were down 5% from 2008, and far shy of the 70K to 80K they expected. This was supposed to be a year with rabid enthusiasm, and that hasn't materialized- not just Colorado, but especially in the other states which were down ~25% from 2008. Missouri was down 56%.
With as bitterly strident as Obama's critics are, it's confounding why they haven't shown up to pick a horse (other than online forums). Probably more a function of a poor field of candidates, but that wasn't supposed to be an issue in the "anybody but Obama' election. Maybe they'll turn out for the General, but I wouldn't say this primary season has been encouraging.
Fun fact #1:The only candidate to improve his vote count from 2008 in all the primary states is Ron Paul, but his support is still fairy small.
CO county-by-county results: Colorado Republican Presidential caucus results