PHOENIX (AP) — Nearly 100,000 voters who haven’t submitted citizenship documents might be prevented from participating in Arizona’s state and local elections, a significant number for the battleground state where races have been tight.

The announcement Tuesday of an error in state-run databases that reclassified voters comes days before county election officials are required to mail ballots to uniformed and overseas voters.

Democratic Secretary of State Adrian Fontes and Stephen Richer, the Republican recorder for Maricopa County, disagree over whether the voters should have access to the full ballot or the ability to vote only in federal races.

Arizona is unique among states in that it requires voters to prove their citizenship to participate in local and state races. Those who haven’t but have sworn to it under the penalty of law are allowed to participate only in federal elections.

Arizona considers drivers’ licenses issued after October 1996 to be valid proof of citizenship. However, a system coding error marked 97,000 voters who obtained licenses before 1996 — roughly 2.5% of all registered voters — as full-ballot voters, state officials said.

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While the error between the state’s voter registration database and the Motor Vehicle Division won’t impact the presidential race, that number of voters could tip the scales in hotly contested races in the state Legislature where Republicans have a slim majority in both chambers.

It also could affect ballot measures before voters, including the constitutional right to abortion and criminalizing noncitizens for entering Arizona through Mexico at any location other than a port of entry.

Fontes said in a statement that the 97,000 voters are longtime Arizonans and mostly Republicans who should be able to fully participate in the general election.

Maricopa County Recorder Stephen Richer, who said his office identified the issue earlier this month, said he plans to sue Fontes’ office Tuesday afternoon, asking a court to classify the voters as federal-only.

“It is my position that these registrants have not satisfied Arizona’s documented proof of citizenship law, and therefore can only vote a ‘FED ONLY’ ballot,” Richer wrote on the social platform X.