New York lawmakers have voted to legalize same-sex marriage -- making their state the third to pass gay marriage through a legislative act and without court action or a vote by the people.

The measure narrowly cleared the Republican-controlled state Senate late Friday by a 33-29 vote. Democratic Gov. Andrew Cuomo, who campaigned on gay marriage last year, signed the bill into law just before midnight.

While gay rights activists hope the latest victory will spill over into other states, conservative groups have already started campaigns against the decision.

The National Organization for Marriage has pledged to commit "at least $2 million" in the upcoming election season to hold GOP politicians accountable for supporting gay marriage.

"The Republican Party has torn up its contract with the voters who trusted them in order to facilitate Andrew Cuomo's bid to be president of the U.S," said NOM president Brian Brown.

"Selling out your principles to get elected is wrong. Selling out your principles to get the other guy elected is just plain dumb," he added.

Shortly before Friday's vote, wavering GOP Sens. Stephen Saland and Mark Grisanti announced they would cross party lines to support the bill.

"While I understand that my vote will disappoint many, I also know my vote is a vote of conscience," Saland said before the bill's passage.

Vermont and New Hampshire also legalized gay marriage through a legislative act.  New York is now the sixth -- and largest -- state where same-sex couples can wed.