California's Proposition 8 ballot question was supported by 52 percent of voters.

"We caused Californians to rethink this issue," Proposition 8 strategist Jeff Flint told the Los Angeles Times. The campaign was the most expensive referendum in the country with the two sides spending more than $74 million.

Eighteen-thousand gay couples reportedly have wed since the ruling made same-sex marriage legal in California 4 1/2 months ago. The Times said the decision to overturn the ruling may put the legality of those unions in jeopardy.

The question on the ballot in Florida asked whether the state should define marriage as the legal union of one man and one woman as husband and wife, and provide that no other legal union that is treated as marriage or the substantial equivalent shall be valid or recognized.

A majority of Arizona voters also showed support for a similar measure to ban gay marriage in their state, CNN said.

In related news, Arkansas voted for a referendum that would prevent gay couples from adopting children, the news network said.