Bennet's win in a Republican year is no more evidence that Colorado is Dem-leaning than Robb's win in Virginia was in 1994. Also consider that Gary Hart narrowly won a second term in Colorado in 1980, and no-one would have called Colorado a Dem-leaning or even a swing state then.
Udall should still be the favourite in a neutral or moderately pro-GOP year, however, if Obama is re-elected it'll be a second midterm, historically bad (though I'm not sure if the first one being bad makes the second being bad less likely).
Hickenlooper also got over 50% of the vote for governor. I do think something fundamental is changing in CO. I would expect 2014 to go against whoever is the incumbent president's party, but hey, Clinton actually had Dem gains during his second midterm, but not enough to retake anything.
