SAN FRANCISCO — Dozens of Republicans have signed on to a legal brief in the U.S. Supreme Court opposing California’s ban on same-sex marriage, including Hewlett-Packard CEO Meg Whitman, who supported Proposition 8 during her unsuccessful 2010 run for governor.

The American Foundation for Equal Rights, which is leading the legal fight against Proposition 8, on Tuesday revealed the growing list of conservatives who are supporting the brief, which is expected to be filed in the Supreme Court on Thursday.

“I feel the time has come to bestow marriage equality to same-sex couples,” Whitman observed in a Linkedin post.

The high court will hear arguments in the Proposition 8 challenge on March 26 and consider the legality of the federal ban on same-sex marriage benefits the next day.

The friend-of-the-court brief will be filed on behalf of two same-sex couples who have challenged California’s 2008 voter-approved ban on gay marriage. The Supreme Court is reviewing an appeals court’s decision last year finding the law unconstitutional.

Among the Republicans signing onto the brief are Ken Mehlman, former chairman of the Republican National Committee who revealed in 2010 he is gay; former California U.S. Rep. Mary Bono Mack; Stephen Hadley, national security adviser under President George W. Bush; former Utah Gov. Jon Huntsman; former Massachusetts Gov. William Weld; and former New Jersey Gov. Christine Todd Whitman.

The Republican backing may have some connection to Theodore Olson, U.S. solicitor general under George W. Bush. Olson has been an outspoken supporter of gay marriage rights since taking on the Proposition 8 case in 2009.

All groups supporting the challenge to Proposition 8 are due to file their legal briefs on Thursday. The White House is weighing whether to take a position by that date.