Trump Plan to Deport 11 Million Immigrants Sells in Iowa

But 45 percent of Republicans who back other candidates say it's a bad idea.

Inside the Poll Numbers: Iowa’s Hidden Winners and Losers

Nearly half of Iowans likely to attend the state's Republican presidential caucuses agree with Donald Trump's call to deport 11 million undocumented immigrants, the latest Bloomberg Politics/Des Moines Register Iowa Poll shows. Among those backing the billionaire in the state hosting the nation's first nomination balloting on Feb. 1, it's even higher, 73 percent.

The numbers offer yet another explanation for why Trump has surged ahead in Iowa and nationally, even if he has yet to provide many details on how his proposed mass deportation would work. It would cost between $400 billion to $600 billion and it would take 20 years to remove those immigrants living in the country illegally, according to the conservative-leaning American Action Forum.

Of Trump's rivals, former Florida Governor Jeb Bush has been the most forceful in pushing back against the proposal, saying the idea is "not realistic and it does not embrace American values."

Backers of the various Republican candidates challenging Trump are more skeptical of his deportation proposal. Of non-Trump supporters, 40 percent say it's a good idea; a plurality, 45 percent, say it's a bad one.

Read poll questions and methodology here.

At the same time, when given a list of issues and asked to rate whether they represent strengths or weaknesses for Trump, two-thirds of all likely Republican caucus-goers listed "dealing with immigration" as one of his strong suits. This includes 90 percent of his supporters and 59 percent of those backing another candidate.

Trump poll question 16: trump-q16

"You can't do it all at once, but if they are illegal, they shouldn't be here," said Gerry Thronson, 64, a retired office worker from Davenport, Iowa.

Thronson said she plans to caucus for Senator Ted Cruz of Texas or retired neurosurgeon Ben Carson. "I'm not a Trump fan," she said. "He's a blowhard, but I love the conversation that he's creating about immigration."

"This is a touchstone issue at this point in the campaign," said J. Ann Selzer, president of West Des Moines-based Selzer & Co., which conducted the poll.

Patrick Messmore, a Republican construction equipment sales manager planning to back Trump, said he realizes the proposal is "pretty extreme." Still, he said he's ready for such actions because he believes too many new arrivals are getting benefits without paying taxes.

"There are a lot of undocumented immigrants in the country that aren't necessarily holding up their end of the bargain," said Messmore, 32, who lives near Grundy Center. "Something needs to change."

The survey, taken Aug. 23-26, included 400 likely Republican caucus participants. On the full sample, it has a margin of error of plus or minus 4.9 percentage points.