Foes of a law that mandates schools teach about the historical contributions of gay, lesbian, bisexual and transgender people have one day left to gather enough voter signatures for a repeal effort.

Starting as early as the 2013-14 school year, Senate Bill 48 (SB48) or the FAIR Education Act, sponsored by state Senator Mark Leno, a Democrat from San Francisco, requires the California Board of Education and local school districts to include the curriculum in their lesson plans.

Opponents of the law have until tomorrow to collect the signatures of 504,760 registered voters to qualify for the next statewide ballot.

Karen England, executive director of the Capitol Resource Institute, the group spearheading the Stop SB48 campaign, told the San Francisco Chronicle that she was confident her group would qualify for the referendum.

But the group sounded less confident in recent emails to supporters.

“The news is not good,” the group wrote on Tuesday. “Finally with two days in a row of no mail delivery, collection points around the state were able to get a good estimate of how many signatures we have in hand. While we expect to have a large amount arrive today and even Wednesday it is doubtful we will get the number of signatures we need to qualify.”

“From all appearances, we would need a miracle to qualify this referendum. But many of those close to the referendum campaign believe in miracles and want to fight until the very last minute. Are you in?”

Supporters of the law note that national conservative organizations have largely kept out of the fight, leading to the speculation that they are planning a November 2012 ballot initiative.

“We always imagined they would try to take another bite at the apple in November,” said Rebekah Orr, a spokesperson for Equality California, the state's largest gay rights group. “If they don't qualify in a few days, then we need to be prepared for them to qualify in November.”

(Related: Group accuses foes of California gay history law SB48 of tricking voters.)