DES MOINES — As the Iowa caucus fast approaches, Ted Cruz's campaign is embroiled in a controversy over a mailer to potential caucus-goers that has drawn a rebuke from the state's top election official.

The mailers purported to be an "official public record" grading the recipients A through F on their voting frequency, with an encouragement to caucus Monday in order to improve their score. The mailer accuse recipients of a "voting violation" in all capital letters, warning, "A follow-up notice may be issued following Monday's caucuses."

The notices come from Cruz's campaign in order to encourage people to turn out. They are not official documents from the state, which is why they have been publicly denounced by the secretary of state.

Iowa Secretary of State Paul Pate, a Republican, released a statement saying the mailer "misrepresents the role of my office and, worse, misrepresents Iowa election law."

"The Iowa Secretary of State's Office never 'grades" voters," Pate said in the statement. "Nor does the Secretary of State maintain records related to Iowa Caucus participation. Caucuses are organized and directed by the state political parties, not the Secretary of State, nor local elections officials."

Caucus participation and voting in general are entirely voluntary. "There is no such thing as an election violation related to frequency of voting," said the secretary of state. "Any insinuation or statement to the contrary is wrong and I believe it is not in keeping in the spirit of the Iowa Caucuses."

Some Cruz supporters initially labeled the mailers a hoax. Steve Deace, the prominent Iowa conservative commentator who has endorsed the Texas senator for president, tweeted "the whole story is fake" and that outlets reporting it had been deceived. But the campaign acknowledged sending the mailers. Deace subsequently acknowledged the error.

The controversy comes as Cruz is caught in a tight fight with both Donald Trump and a rising Marco Rubio to win Iowa. Cruz is currently second in the Washington Examiner's presidential power rankings, with Trump and Rubio in first and third place, respectively.

"I had some voters mention to me they were upset about it," Rubio told reporters in Ames Saturday. "Obviously, they had people's names and they gave them 'F' ratings for how they voted. I think a lot of voters were disturbed by it and again, it's kind of an unusual way to end your campaign in the state."

Iowans vote Monday.