ABC News’ Michael Falcone, Emily Friedman and Shushannah Walshe report:

DES MOINES — Signaling that he plans to compete more aggressively for votes in Iowa, Mitt Romney’s presidential campaign has been organizing tele-town hall meetings in the state criticizing rival Rick Perry’s stance on immigration.

On Thursday night, the Romney campaign placed phone calls to thousands of Iowans inviting them to participate in a telephone town hall-style meeting with Arizona Sheriff Paul Babeu, a Romney supporter.

“Rick Perry is opposing a border fence and granting in-state tuition benefits to illegal immigrants. Rick Perry is part of the illegal immigration problem,” Babeu said in a voicemail message to Iowans who did not pick up their phones when the automated phone calls were made.

Those who did answer were able to listen in to a live meeting with the border-state sheriff. The calls took place at about 7 p.m. Central time on Thursday.

The phone calls, which were paid for by the Romney campaign, indicate that the former Massachusetts governor is not taking Iowa for granted. He campaigned hard here during the 2008 primary season, but four years later his campaign has been reticent to take an “all in” approach. The calls also show that the Romney team considers Perry to be their chief opposition in the state, but is largely dismissing Herman Cain, who landed at the top of a recent poll of Iowa Republicans.

Romney, who has not visited the state since Oct. 20, will return to Iowa on Monday and plans to hold several events in the Eastern part of the state, which will hold the nation’s first presidential caucuses on Jan. 3, 2012. Perry has spent three days in Iowa already this week and he will speak at a dinner sponsored by the Iowa Republican Party in Des Moines on Friday night.

According to a recent Des Moines Register Poll, Romney and Cain are essentially tied for the lead in Iowa — Cain with 23 percent support compared to Romney’s 22 percent. Perry wound up in a distant fifth place, tied with New Gingrich, at 7 percent. The poll was release just one day before news of sexual harassment allegations against Cain broke.

Still, the Perry campaign has significant financial resources and the Texas governor recently went on the air with television and radio advertisements in the Hawkeye State. (Neither of  those spots specifically attack Romney.)

Romney campaign officials said they have had “a couple” of similar telephone town-hall meetings featuring Sheriff Babeu. When asked if there were more to come, a top Romney strategist in Iowa told ABC News: “Stay tuned.”

The Romney campaign announced the Pinal County sheriff’s endorsement in mid-October.

“His efforts working to protect our border are critical to lowering crime, reducing illegal immigration, and stopping both drug and human trafficking,” Romney said in a statement announcing the Arizona lawman’s backing. “Sheriff Babeu has been a leader in the call for the federal government to secure the border.”