SACRAMENTO, Calif. (AP) – Supporters of an effort to repeal California’s new law requiring mandatory vaccines for schoolchildren are facing a Monday deadline for a ballot initiative asking voters to repeal the law.

The group has until the end of the day to submit the needed 366,000 signatures to ask California voters to repeal SB277.

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Gov. Jerry Brown signed the bill into law earlier this year amid fierce opposition from some parents’ rights groups who say the state should not force their children to be vaccinated.

It’s unclear whether supporters have enough signatures to make it to the ballot. The proponent of the effort, former Assemblyman Tim Donnelly, said in an email Monday that volunteers were coerced and threatened while collecting signatures.

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Donnelly did not return repeated messages inquiring about the effort’s chances.