A survey of more than 3,000 California residents has found that one in four has become more supportive of gay marriage.
Only eight per cent said they had become more opposed.
The poll, conducted by the Washington, DC-based Public Religion Research Institute, found that a majority (51 per cent) of respondents would vote in favour of gay marriage if a vote was held.
California legalised gay marriage in 2007 but only a few months later, opponents succeeded in having the right voted down in a state-wide referendum, also known as Proposition 8.
The survey found that only 22 per cent of those questioned thought Prop 8 was a good thing for the state, while 29 per cent said it was a bad thing and 45 per cent said it made no difference.
Support levels for gay marriage jumped significantly when respondents were asked if they would support a law that only allowed civil ceremonies. Sixty-one per cent said they agreed with this.
The overwhelming majority of Californians – 75 per cent – said they were in favour of laws which protect against homophobic discrimination in the workplace, while 69 per cent support out gay soldiers in the military and 56 per cent agreed with gay couples adopting children.
The poll also found striking differences in who supports marriage equality.
While 57 per cent of Latino Catholics said they would vote for marriage equality, only 22 per cent of Latino protestants said they would not.
Six in ten religious respondents who heard positive messages from clergy on gay equality were in favour of allowing gay couples to marry, while another 22 per cent supported civil unions.
However, those who reported hearing negative messages from their clergy had far lower levels of support, with only 19 per cent supporting same-sex marriage and almost rejecting all legal recognition of gay relationships.
The Public Religion Research Institute surveyed 3,351 Californian adults between June 14th-30th 2010 by telephone.