What do you mean by “undervote”? The number of people polled who say they support Obama but actually WON’T vote for him? If so, nothing is built into the analysis for that, although, I think that is a valid factor.
Don’t be surprised if Colorado is a manifestation of wishful liberal thinking. Bush won it by 5% in 2004. A 6% swing in 4 yrs is rather a lot to expect without some huge demographic swing due to a natural disaster emptying a city.
(Which btw is why the earthquakes west of Reno are worrisome. Reno is all that keeps Nevada red.)