Colorado and the West are at play for more reasons than the dynamism at the top of the Democratic ticket. In fact, there's a sea change washing across the Great Plains: with new demographics in the population, there are new voting blocs remaking the political map, and therefore the Electoral College.
As the New Yorker put it in an upcoming article, The Code of the West:
Since 2002, Democrats have replaced Republican governors in Montana, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Arizona. It is possible to drive from the Canadian border to the Mexican border and not pass through a single state governed by a Republican. “That’s a good pictorial of how you can think about what Democrats have done out here,” Ritter said.