A survey of 672 Californians who are “likely to vote” in November has found that just over half of them oppose a ballot measure banning same-sex marriages.
The Field Poll found that 51% oppose an amendment to the state’s constitution recognising marriage as only between a man and woman.
42% were in favour.
On Wednesday the California Supreme Court rejected a petition filed by gay and lesbian groups asking for the ballot to be removed because it would deny same-sex couples marriage equality.
Campaigners collected 694,354 signatures, enough for a ballot proposition to be put to California voters on the same day as the US Presidential and Congressional elections.
The California Marriage Protection Act would amend the state constitution to define marriage as only “between a man and a woman.”
In May the state Supreme Court ruled that same-sex couples cannot be excluded from marriage.
The weddings began last month. California has the highest number of same-sex couples of any state in the US.
In 2000 voters in California approved Proposition 22 by 61.4% to 38.6%.
It defined marriage as “a personal relation arising out of a civil contract between a man and a woman.”
The May ruling by the state Supreme Court overturned Prop 22.