I don't think there's a very good chance that Colorado goes Democrat. The whirl around recent Democratic gains in Colorado don't signify a shift to the left so much as a trend away from the Republican Party seen across the country. Moderate Democrats have beaten moderate Republicans in Colorado because the GOP brand has been miserable. But Boulder Democrat Mark Udall is much more liberal than the state as a whole--or Gov. Ritter or Sen. Salazar--and he's facing Bob Schaffer, a well-liked conservative that is much closer to Colorado's sweet spot.
Because of the Democratic Convention being in town the media will cause a lot of commotion about this race--but it's mostly posturing.
If John Kerry, a northeastern liberal who ran a terrible campaign could get 47% in 2004, when the national dynamic was much more favorable to republicans, then I think Udall can win in 2008.