How has no one mentioned the only one that really seems to fit: Arizona?
Ya Arizona is the best answer here.
CO's blue lean isn't entirely due to Denver - it also has two pretty large (>100K) college towns and lots of the mountains have blue leans due to destination towns/retirement/recreation towns. Idaho lacks those outside of Sun Valley (Moscow is... not Boulder) and Utah's Native American and Mexican constituencies aren't supplementing any D tilt of SLC area at all. Arizona on the other hand has a pretty sizeable D base outside of Phoenix if you look to Tucson and Nogales and of course the Diné lands.
