Date: September 09, 2013 07:50PM
I think there are a number of reasons, and I'll throw out some thoughts in no particular order.
1. Mormonism is not just a religion, it is a culture and lifestyle. Even for those that have left or inactive, most were raised conservative/Republican.
2. I think something like 90% of TBMs are Republican (if I'm remembering studies correctly). 60% in UT (in name mormon); half active = 30%; 90% of 30% = 27% of votes to start with are Republican TBM. Let's say the remaining 40% are 1/3 R, 1/3 D, 1/3 Independent. That leaves R with about 27 + 13 or 40% to start with.
3. Gerrymandering. Not only does it happen for dividing up for the House of Reps, where being in suburbs south of SLC I did have the one Utah D for a Rep., they gerrymandered me into being with Provo/Orem, so now I have the wackadoodle J. C. for a Rep. It happens with districts for State and House Reps., too. Gerrymander to increase your power. A few non-R can win in local elections, but not enough to make a big difference. See the map for the U.S. House where they have gerrymandered to divide up (more liberal) SLC area by putting parts with strong Republican areas (1, 2, 3).http://elections.utah.gov/map/district-maps
4. There are two parties in Utah. Conservative Republican, and moderate Republican [Democrat]. A moderate Democrat, or liberal Democrat has little hope of winning. [See #1]
5. Get out of the big cities, and some areas (although small) are 90%+ mormon. A few years ago I remember there was one small UT county that had only one registered Dem. Look at all the areas that get representatives in the UT Senate:http://www.utahsenate.org/mapold.shtml
I count 9 of 29 where you can read numbers that are almost guaranteed Republican. They dilute anything that may be coming from more liberal areas around SLC.