It is already the most expensive social issue ballot in US history, with more than $65m donated to both sides of the gay marriage debate.
With just days to go until Californians vote on Proposition 8, the tactics of one of its proponents has been criticised for likening the situation to Germany in the 1930s.
Proposition 8 would amend the state Constitution to “eliminate right of same-sex couples to marry.”
In May the California Supreme Court voted 4 to 3 to strike down the ban, ruling that lesbian and gay couples are entitled to the same fundamental right to marry as heterosexual couples as protected by the California constitution.
Brad Dacus of the conservative Pacific Justice Institute stood on the steps of the state Capitol in Sacramento this week and said:
“There was another time in history when people, when the bell tolled. And the question was whether or not they were going to hear it.
“The time was during Nazi Germany with Adolf Hitler. You see he brought crowds of clergy together to assure them that he was going to look after the church.
“And one of the members, bold and courageous, Reverend Niemoller made his way to the front and … said, ‘Hitler, we are not concerned about the church. Jesus Christ will take care of the church. We are concerned about the soul of Germany.’
“Embarrassed and chagrined, his peers quickly shuffled him to the back.
“And as they did Adolf Hitler said, ‘The soul of Germany, you can leave that to me.’ And they did, and because they did bombs did not only fall upon the nation of Germany, but also upon the church and their testimony to this very day.
“Let us not make that mistake folks. Let us hear the bell! Vote on Proposition 8!”
The Anti-Defamation league expressed outrage at Mr Dacus’ words.
“No matter what position one takes on this controversial contemporary moral and political issue, this analogy is hurtful and inappropriate,” the group, which fight anti-Semitism, said in a statement.
“We should not lose sight of the fact that six million Jews perished in the Holocaust.
“Unfortunately, it has become all too easy for some advocates of various political positions to suggest that their opponents are like the Nazis. Such comparisons are profoundly hurtful and should be off limits.”
The Pacific Justice Institute describes itself as a “legal organisation specialising in the defence of religious freedom, parental rights, and other civil liberties.”
It has led campaigns against schools who try to embrace diversity and reflect the lives of LGBT-led families and has erroneously claimed that Proposition 8 will have some effect on education in California.
“Opponents of traditional marriage keep telling us that Prop 8 has nothing to do with education,” Mr Dacus claimed.
“In reality, they want to push the gay lifestyle on kindergartners, and we can only imagine how much worse it will be if Prop 8 is defeated. This is not a scenario most Californians want replayed in their elementary schools.”
The most recent Field Poll found 49% of likely voters oppose Proposition 8 and 44% support it, with 7% undecided.
On Wednesday the state’s Governor, Arnold Schwarzenegger, said he would be voting no on Prop 8. His wife Maria Shriver said earlier this week:
“I believe in people’s right to choose a partner that they love, and that’s a decision that I have come to, and I have felt that way for a long time.”
Californians will vote on Prop 8 on Tuesday.