No Republican legislator signed the petition, though Gov. Arnold Schwarzenegger, a Republican, denounced the anti-gay marriage measure over the weekend.
With almost 11 million ballots tallied, Proposition 8 had 52.3% of the vote to 47.7%. Although many ballots remain to be counted, the 500,000-vote spread is viewed as insurmountable.
"The citizens of California rely on the Legislature and the courts to safeguard against unlawful discrimination by temporary, and often short-lived, majorities," the legislators said in the document, written by attorneys at the firm Gibson, Dunn & Crutcher.
"This is a Hail Mary, no question about it," said Frank Schubert, manager of the Proposition 8 campaign.
Atty. Gen. Jerry Brown's office would be obligated to defend the initiative. But Schubert said that if the high court agrees to hear the case, backers of the initiative would seek to intervene to defend it.
In their brief, lawmakers described the 500,000-vote margin as a "bare majority," and said it was "compromising the enduring constitutional promise of equal protection under the law."
"Proposition 8 seeks to effect a monumental revision of this foundational principle and constitutional structure by allowing a bare majority of voters to eliminate a fundamental right of a constitutionally protected minority group," the brief says.
"If Proposition 8 takes effect, this court will no longer be the final arbiter of the rights of minorities," it continues.
The action contends that the ban, created by the initiative that defines marriage as being between one man and one woman, cannot be done by a mere constitutional amendment. Rather, it must be done by a revision of the entire Constitution and the Legislature would have to be involved.
As advocates of same-sex marriage turn to courts, protests, and perhaps a future ballot measure in an attempt to overturn Proposition 8, Schubert declared that the vote is "as over as Barack Obama's election."
The chief strategist for Proposition 8 said the best way to overturn the measure would be to place an initiative on the ballot that would repeal it. But he doubts that will happen.
"Politically, this was the best chance they could have possibly had," Schubert said of the measure's opponents.
The all-important ballot title written by Brown cast the measure as one that would revoke a right, a move that had been viewed as particularly helpful to opponents.
Also, Schubert noted, there was a huge Democratic turnout -- although many Democrats, particularly African Americans and Latinos, don't support same-sex marriage and voted for Proposition 8. Exit polls showed blacks supported the measure 70% to 30%.
One of the closing ads featured Sen. Dianne Feinstein (D-Calif.). Popular though she is, Schubert said, it was odd that Proposition 8 foes would select Feinstein to lecture voters, including minorities, about discrimination.
"It had the feel of a lily white, liberal campaign," Schubert said.