FACTBOX: Presidential candidates' views on gay marriage

(Reuters) - The California Supreme Court overturned a ban on same-sex marriages on Thursday in a ruling that could clear the way for homosexual couples to marry in the most populous U.S. state.

Massachusetts has been the only U.S. state to allow gay marriage.

Same-sex marriage, one of the most divisive issues in recent U.S. politics, has mobilized millions of socially conservative Christian voters to support candidates who oppose it.

Here are the U.S. presidential candidates' positions on same-sex marriage.

DEMOCRATIC SEN. BARACK OBAMA, CAMPAIGN STATEMENT

"Barack Obama has always believed that same-sex couples should enjoy equal rights under the law, and he will continue to fight for civil unions as president. He respects the decision of the California Supreme Court, and continues to believe that states should make their own decisions when it comes to the issue of marriage."

DEMOCRATIC SEN. HILLARY CLINTON

Opposes same-sex marriage but supports civil unions that confer the same legal rights that married couples have.

REPUBLICAN SEN. JOHN MCCAIN