Opponents of Arizona's school-voucher expansion delivered more than 111,000 petition signatures to the secretary of state's office Tuesday, the first big step toward forcing a statewide vote next year to overturn the law.

With the petitions' delivery, the law has been put on hold while the signatures are certified by the secretary of state's and county recorders' offices. That should take about 40 days.

The grass-roots group Save Our Schools relied on volunteers statewide to gather 111,540 signatures in just three months. A total of about 75,000 signatures were required.

PREVIOUSLY: Signatures aim to derail private school voucher law in Arizona

Elections experts say a cushion of about 30 percent is a rule of thumb, given that thousands of signatures are typically ruled invalid. The Save Our Schools cushion is almost 50 percent.

"When you're out there with volunteers, not everyone follows the rules, probably unintentionally much of the time," said Joe Kanefield, a campaign law attorney and former state elections director.

Legal challenges to the signatures are expected.

It's also possible that the Republican supporters of the voucher expansion, passed during the legislative session last spring, could repeal the law next year, to avert a potential defeat at the ballot box in November 2018.

Republicans took that evasive action three years ago, when faced with another challenge to a state law.

Back in 2014, Republicans repealed a controversial elections law passed the year before, after opponents got enough signatures to put it to a statewide referendum.

The school-voucher expansion would allow all Arizona families to use state tax dollars to pay for a child's education at private or religious schools, through so-called Empowerment Scholarship Accounts.

The law would allow 5,500 new students per year to join the program, with a cap of 30,000 by 2022.

SOS and other opponents argue the state is taking money away from underfunded public schools to help wealthier families give their children a private-school education.

Public-school advocates point to the legislation out-of-state backers, including the American Federation for Children, as a sign that Arizonans are not demanding school vouchers.

At a June donor retreat organized by the Koch brothers, Gov. Ducey credited the "Koch network" with helping him expand vouchers. “I needed the power of the network," he said.

Republican State Sen. Debbie Lesko shepherded the voucher expansion through the state Legislature, and was saluted for it by Education Secretary Betsy DeVos.

Lesko issued this statement Tuesday after SOS Arizona delivered its petitions:

“I feel sorry for the parents who are waiting to use the new ESA expansion to help their child start a new school this year. They are now being put on hold wondering what to do.

Unlike parents who can afford to move to a good school district or can afford to send their kids to private school, these moms need the help of the ESA.

I support public schools AND I support giving more choices to parents. I hope someday opponents of my legislation realize we can do both and will work with me to improve education for everyone so no other Arizona parents have to feel the way they do today.”

There were several ESA families near the Capitol gathering Tuesday where Save Our Schools celebrated the petition drive.

Many were there because they had signed up their children for the program this year, but were now shut out because the law was on hold.

A representative of the American Federation for Children said the Phoenix Catholic Diocese had offered to cover the children's tuition while the referendum campaign played out.