Republican presidential candidate Mitt Romney, whose Mormon faith played a big role in his primary victory in Utah, won 36 delegates in a winner-take-all sweep, while Barack Obama defeated Hillary Rodham Clinton in the Democratic primary.
Romney had been expected to win the state, where more than 60 percent of residents are also members of The Church of Jesus Christ of Latter-day Saints. He also won the GOP primary in Massachusetts, where he served as governor.
Obama, an Illinois senator, held a commanding lead with the state's Democratic primary voters. Utah Democrats split their delegates by the popular vote.
The Associated Press made its call based on surveys of voters as they left the polls.
Romney is a favorite adopted son in Utah. He was chief of the Salt Lake Olympics in 2002 and owns a vacation home at Park City's Deer Valley resort.
About 90 percent of Republicans at Utah polls said they were Mormon and that Romney shared their values.
"Honestly, yes, I'm voting for him because he's LDS," said Laroy Whitmore, a 40-year-old construction worker from the Salt Lake City suburb of Sandy.
"But I was impressed with the Olympics. I thought it was dead, but he came in and fixed it," Whitmore added. "Clearly, he has the background and experience to lead our country."
Obama had an edge with male voters in Utah, while women appeared evenly divided between him and Clinton, a New York senator.
Voters who described themselves as independents were more than twice as likely to vote for Obama, the survey found.