Rick Santorum is scheduled to meet with gay marriage foes in Washington state on Monday, the same day Governor Chris Gregoire is holding a signing ceremony for a bill legalizing gay marriage in the state, The Seattle Times reported.

Gregoire will sign the bill into law at 11:30AM, making Washington the seventh state to legalize gay marriage.

The Democrat-controlled House approved the measure with a 55-43 vote on Wednesday, a day after a federal court declared California's gay marriage ban, Proposition 8, in violation of the United States Constitution, and one week after the Washington Senate passed the measure with a wider margin than expected.

Santorum, considered the GOP presidential field's most vocal opponent of giving gay couples the right to marry, will meet with opponents of the measure in Olympia in the afternoon. A 7PM campaign rally is scheduled at the Washington Historical Museum in Tacoma.

Opponents have already begun an effort to repeal the measure at the ballot box. But voters in 2009 rejected a ballot question aimed at repealing the state's domestic partnership law, which gives gay and lesbian couples all the protections of marriage without the name.

If opponents gather sufficient signatures to put the law up for a vote, its June start would be put on hold pending the outcome of a November election.

Washington holds its presidential caucuses on March 3.