PHOENIX (AP) - Opponents of Arizona's sweeping new universal school voucher law are a big step closer to blocking it until voters have their say in the November 2018 election.

The Secretary of State's office determined late Friday that 97 percent of the 111,000 signatures collected by Save Our Schools Arizona passed an initial review. That means county recorders checking a sample of signatures over the next three weeks can reject 30 percent of them and the voter referendum will still make the ballot.

State Elections Director Eric Spencer certification is fairly likely. He said backers "should be pretty confident that at least 70 percent of the people that signed this are actually registered voters."

School voucher backers have already launched a full-court legal effort to contest the signatures and petitions.