Challengers of Washington's newly signed gay-marriage bill have filed a referendum challenge.

Less than four hours after Gov. Chris Gregoire on Monday signed into law the bill authorizing civil marriage for same-sex couples, SB6239, Joseph Backholm of Preserve Marriage Washington filed Referendum 73 seeking to overturn the law.

Actually, R-74 is the new number for Washington's gay marriage referendum. It turns out that R-73 was assigned last spring to a campaign challenging last year's medical marijuana law; nothing came of that effort.

Backholm, who has the backing of a number of in-state and national organizations, said it will be an expensive and hard-fought campaign, but that he expects to prevail.

"I don't think it's that hard of a case to make," he told reporters at the Office of Secretary of State. "There are lots of meaningful relationships that are not called marriage. Marriage should be reserved for a man and a woman and the children they raise."

Christopher Plante of the National Organization for Marriage, said each side will spend $2 million-$6 million getting their message out. Backholm said, "I'm very confident."

It's likely to be early March before R-74 sponsors can print and circulate petitions. Their deadline for turning in 120,577 valid signatures is June 6. That is one day before the new law, SB6239, ordinarily would have taken effect.

The submission of signatures suspends the law from taking effect until after signature verification and, if qualified with enough valid signatures, until the election is conducted this fall and certified by Dec. 6.

The referendum simply takes the exact language of the bill that the Legislature passed and Gregoire signed, and places it on the ballot. The voter's choice will be to affirm the law or to reject it – so essentially the sponsors who are bringing the referendum forward will be asking for a "reject" vote on their own measure. Supporters of gay marriage will be asking for a vote to affirm the law.

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