CEDAR RAPIDS, Iowa (AP) — Iowa's top elections administrator has accused some county officials who tried to make it easier to vote by mail during the pandemic of illegally breaching voters' personal information, court filings revealed Wednesday.

The assertion by Secretary of State Paul Pate, a Republican, is a victory for President Donald Trump's reelection campaign, which is suing three Iowa counties to invalidate at least 70,000 returned absentee ballot request forms.

The claim comes ahead of a hearing Thursday in a lawsuit filed by the Trump campaign and state and national GOP groups against Linn County Auditor Joel Miller.

The lawsuit seeks to nullify about 50,000 requests for absentee ballots that have been returned since July, when Miller's office sent forms that were pre-filled with personal information to about 140,000 registered voters. Voters just had to review, sign and return them to request ballots that will be mailed out beginning Oct. 5.

The Trump campaign is seeking a temporary injunction that would require those returned forms to be thrown out and voters to fill out new blank forms on their own.

Similar lawsuits by Trump's campaign and GOP groups are seeking to invalidate ballot requests in Johnson and Woodbury counties, where at least 20,000 such forms have been returned.

Iowa is expected to be a competitive race in the presidential election between Trump and Democrat Joe Biden, and the dispute over absentee ballots threatens to be disruptive to determining the winner. Trump's campaign has warned that any ballots cast in response to the pre-filled mailings will be subject to legal challenge.

Linn County has accused the Trump campaign and GOP groups of attempting “voter suppression" with the lawsuit and argued that its elected auditor has acted lawfully.

Miller has said that he sent the forms with voter information, including drivers' license or voter verification numbers, to promote absentee voting as the coronavirus spreads across Iowa.

A new law passed by the Republican-controlled Legislature in June blocks county auditors from using their databases to fill in routine gaps in such forms, including identification numbers that are required but many do not know. Instead, auditors are required to contact such voters by email and mail to fill in such information themselves — a time-consuming process that local officials say could disenfranchise individuals or force them to vote in polling places that are at risk for virus transmission.

GOP supporters say that it's a key absentee ballot safeguard to have voters fill in information on their own.

Miller notified the secretary's office of his plan to mail forms with such information pre-filled on July 11 and gave Pate the chance to raise objections. The county's mailing concluded in late July.

On July 17, Pate issued a directive to auditors saying that all such mailings must be sent blank in order to ensure uniformity across the state.

On Tuesday evening, Pate's office sent Miller a “notice of technical infraction” and asked Democratic Attorney General Tom Miller and Linn County Attorney Jerry Vander Sanden to investigate the mailings further.

“This is a clear violation of Iowa law by Auditor Miller,” Pate wrote to Tom Miller on Tuesday. Pate enclosed a legal analysis by his office that claimed Linn County did not have a “legitimate purpose” to access and include voters' personal information in the mailings.

The letter said that the mailings in Johnson and Woodbury counties remained under investigation. As for Linn County, Pate told Tom Miller that he was prepared to issue a “notice to all affected registered voters at the conclusion of your investigation."

A lawyer for Trump's campaign filed the state's letter and analysis in court as part of its legal arguments ahead of Thursday's hearing.