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.
Fun Fact Jeff flake actually lost Arizona outside Maricopa in 2012. In 2018 the opposite was true.
