Polling shows that 71 per cent of Utah voters support some form of legal recognition for gay couples.
The survey, by Brigham Young University, found that 43 per cent of respondents thought civil unions should be legal, while 28 per cent wanted full marriage equality.
Just 29 per cent were opposed to any form of legal recognition, a substantial drop from 54 per cent in 2004.
The total percentage against marriage equality, including those who support civil unions as an alternative, was 72 per cent.
Chris Karpowitz, a political science professor at Brigham Young University, told the Deseret News that the poll showed “massive change”.
He said: “Utah is seeing the same kind of movement that we see in the United States generally.
“We’re getting massive change in public opinion in a very short period of time.”
Mr Karpowitz added that the difference with Utah voters is that they are moving “not toward full support of marriage equality but toward civil unions”.
The survey was based on election exit polls and surveys of voter panels derived from exit polls.