The campaign literature, paid for by the Texas senator’s campaign, is labeled "Voter Violation" in bold red letters, with the words "official public record" across the top.
The letter lists the name of the resident -- as well as the specific names of their neighbors -- along with a grade for how often they’ve voted.
"Their scores are published below and many of them will see your score as well." the mailer says.
The Cruz campaign came under fire from Iowa election officials, who blasted the mailer as misleading.
"Today I was shown a piece of literature from the Cruz for President campaign that misrepresents the role of my office, and worse, misrepresents Iowa election law," Iowa Secretary of State Paul Pate said in a statement.
He added there is no such thing as a violation based on infrequent voting.
"Listen, Matt Schultz, who is a former secretary of state, is a chairman of our campaign, put out a public statement saying these mailers are routine. That the Iowa Republican Party has done in the past, in past elections and I will apologize to nobody for using every tool we can to encourage Iowa voters to come out to vote," Cruz told reporters Saturday evening.
"It's kind of an unusual way to end your campaign in a state," Rubio said. "It sounds like he's under a lot of pressure and maybe not reacting very well to it, which is problematic."
The Florida senator is circulating a similar mailer, framed as a "report card." However, his literature does not imply a "voting violation," nor does it list the voting frequency of neighbors by name.
Tom Hinkeldey, a resident of Alta, Iowa, said Cruz dragged "me and my neighbors’ names through the mud" by sending out the mailer.
"It was just a little perturbing that a candidate would send that out, thinking that it would, in any way, have the reaction that I should go vote for this guy," he said. "The people on that list are good people. He doesn't know them. He doesn't know our community."
Hinkeldey, who hasn’t caucused before, said he was undecided before the mailer, but now plans to caucus for Rubio.
ABC News' Jessica Hopper and Ines DeLaCuetara contributed to this report.