South Carolina, Texas, Utah
In that order. First two will be close though.
Utah? 
Only if a Democratic Mormon ran.
Colorado is only about 2% Mormon though. Yes, Utah non-Mormons are very Democratic, but I suspect a lot of that is oppositional voting. If Mormons were reduced to a minority and no longer dominated the states' politics, I'd guess the non-Mormons Utahns would start voting somewhat similarly to non-Mormon Coloradans, leaving the state still quite Republican.
I think all non-mormons will be voting as opposition until the first Dem victory in Utah which would be between 2025-2035, but I think the Hispanics being the biggest voting block in Utah after that would make it blue.
Poll
