Republican presidential candidate Mitt Romney won 36 delegates in a winner-take-all sweep of Utah, while Barack Obama defeated Hillary Rodham Clinton in the Democratic primary.
Romney, a Mormon like more than 60 percent of Utah residents, had been expected to win in Utah, adding to his primary win 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.
In Utah, Romney found favor with GOP voters who said the economy and immigration were their main concerns, according to exit polls conducted for The Associated Press.
"It's always great when the people who know you best support you," said Josh Romney, 32, one of the candidate's five sons, who lives in Salt Lake City and works for a real-estate development firm.
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.
"There's something going on with Obama," said Utah Democratic Party spokesman Bill Keshlear, describing Obama's appeal.
"It has to do with his youth, his message of hope and enthusiasm. Part of it is generational. A lot of people his age and younger who grew up with hip-hop culture are comfortable with an African-American as president," he said.
Because of Romney's overwhelming support among Utah Republicans and their winner-take-all primary, Arizona Sen. McCain's campaign and that of former Arkansas Gov. Mike Huckabee have been all but absent in Utah.
Romney, by contrast, has made several fundraising appearances and ran television commercials here. He raised $5.2 million last year for his presidential campaign in Utah, making it his second-highest yielding state after California, according to Federal Election Commission filings.
For Jamelle Chadwick, a stay-at-home mother in Sandy, Utah, Romney's Mormonism made the difference.
"The standards are important in leadership, like integrity, honesty and hard work," she said, adding that Romney's experience is another plus. "He knows how to solve problems."