A new poll shows the main reason Iowa caucusgoers may be head over heels for Donald Trump. And it can all be summed up in one term: mass deportation.

The poll, from The DesMoines Registerfound that nearly half of Republicans likely to attend the caucus believe that all the undocumented immigrants in the United States should be rounded up and sent back to whatever country they came from.

Not surprisingly, 73 percent of Trump supporters polled are for mass deportation; 40 percent of Republicans backing other candidates are for mass deportation, as well.

This is somewhat peculiar in an agricultural state like Iowa, which depends more and more on immigrant labor for economic survival. When border control toughened in Southwestern states a few years back, crops were left to rot in California and Arizona with no migrant workers to work the fields. If a mass deportation plan were actually to be carried out, Iowa would almost certainly face a similar shortage of helping hands.

As it stands, Trump is the sole leading GOP candidate who openly supports the deportation of all the nation’s undocumented immigrants. Jeb Bush, Ben Carson (with whom Trump is tied in Iowa polls), Carly Fiorina, Mike Huckabee, Rand Paul, Marco Rubio and Scott Walker have all dismissed the idea as impractical. Ted Cruz has avoided answering questions on the subject altogether.

“Impractical” may be one of the best words to describe Trump’s mass deportation scheme. Another word is “expensive.” According to the The American Action Forum, deporting all of America’s immigrants would come with a price tag of at least $419 billion, and reduce the GDP by 5.7 percent. Not exactly fiscally conservative.