This is Utah we are talking about, so the influence of the Mormon church, a.k.a. the Church of Jesus Christ of Latter-Day Saints or LDS Church is a large factor. The graphic below demonstrates opinions on marriage equality separated by religious belief and membership in the LDS church.
Note that among LDS support for marriage equality has been consistently below 10% for the last 8 years, while nearly three-quarters of non-religious folk now support full marriage equality.
One should take note that Republican presidential candidate Mitt Romney is a member of the LDS church, and these numbers may explain his fervent opposition to marriage equality and can help predict how a Romney administration would address the issue of legal recognition for same-sex couples by the federal government. (HINT: it's not good!)
Hat/tip to TowleRoad