West Virginia Secretary of State Natalie Tennant attacked Americans for Prosperity, a conservative nonprofit backed by billionaires Charles and David Koch, on Tuesday for distributing “misleading” and “confusing” voter registration mailings, according to the Associated Press.

The leaflets, sent out to at least eight different counties, warned residents that if they did not update their voter registration before April 22, they could become ineligible to vote in the upcoming May 13 election. The mailer also included a voter registration card and prepaid envelope.

Tennant, who is running for U.S. Senate, warned residents on Tuesday to discard the mailers, clarifying that residents need to update their registration only under three conditions:

If you have not moved, changed your name, or switched political parties, then you should throw this mailer into the trash because your voter registration is still valid. ... We were made aware of this situation because there was a large number of confused citizens calling our office and the offices of county clerks asking questions about why they had to update their voter registration information. The secretary of state’s office did not send this mailer, and it did not come from county clerks. We don’t know what the purpose of the mailer is but we do know that it is confusing citizens.

Berkeley County Chief Deputy Clerk Bonnie Woodall, who oversees voter registration in the county, also described residents as “very confused and duped” by the AFP leaflets.

“They specialized leaflets for each county, which gave people the feeling they would not be able to vote if they did not fill these forms out and get them back to us by today,” Woodall explained.

Americans for Prosperity state director Wendy McCuskey defended the strategy as a “nonpartisan effort” to increase voter registration, while admitting that a “few mistakes” may have been made.

“We identified people who are not registered to vote,” McCuskey told The Charleston Gazette on Tuesday. “We wanted to encourage people who are not registered to participate in voting.”

“There may have been a few mistakes,” McCuskey added, “But we are identifying people who are not registered. It is pretty straightforward. Sometimes, voter files get messed up.”