Pinal County election officials say an error has led to some voters who are registered without a party affiliation to receive ballots for a particular party that they may not have wanted.
Arizona law allows non-affiliated voters who have elected to be on the permanent early voting list to select a ballot from a recognized party if they choose to vote in the primary and receive a ballot by mail.
Voters contacted the county recorder's office and said they had received ballots but had not requested one be sent to them.
In a news release, the recorder's office says the voter system retained the selection of voters from the 2016 election primary and sent that ballot choice to them in the mail. Voters who had contacted the recorder's office during the current election cycle were not affected.
The recorder's office said the error happened due to an "invalid system program" that was used to purge voter selection after the 2016 primary. Voters in two other counties are also affected, though they were not named in a news release from the Pinal County Recorder's Office, which said it had spoken with the recorders in those counties.
"We are all very disappointed in the current vendor's lack of support and look forward to a new voter registration system being implemented in 2019 with a new vendor as the current system is clearly outdated," Pinal County Recorder Virginia Ross said in a statement.
The Maricopa County Recorder's Office said the issue did not affect voters there.
Of the three impacted counties, Pinal has the most voters impacted by the error, officials said, but an exact number remains under investigation with the Arizona Secretary of State.
Those affected have several options: vote the ballot they received, discard the ballot, or contact the recorder's office for the ballot of a different party.
The last day to request a ballot by mail is August 17.