“Turnout is basically what separates Trump and Cruz right now,” said Patrick Murray, director of the Monmouth University Polling Institute, in a statement. “Trump’s victory hinges on having a high number of self-motivated, lone wolf caucus-goers show up Monday night.”

Approximately 45 percent of likely caucus-goers surveyed reported being contacted by a campaign, including a plurality who heard from Cruz. Monmouth found 25 percent of likely caucus-goers heard from Cruz, 17 percent of respondents were contacted by Rubio, 13 percent of those surveyed heard from Trump, and 12 percent reported hearing from the Carson campaign.

The Iowa caucus’ electorate also appears much closer to having made up its mind, as nearly half of all likely caucus-goers have said they are completely decided on who they intend to support, up 20 points since last month.

The poll also shows some good news for the Cruz campaign among the Republican base. Evangelical and “very conservative” voters prefer Cruz most. And while 88 percent of likely caucus-goers heard Iowa Gov. Terry Branstad’s call to vote against Cruz, nearly two-thirds of those who heard it said that it will have no bearing on their vote.

The Monmouth University poll surveyed 500 likely caucus-goers by telephone from January 23 to 26. The poll had a 4.4 percentage point margin of error.

This story was corrected from an earlier version that said Cruz was gaining on Trump. A comparison was incorrectly made to a previous national Monmouth poll rather than the last Monmouth poll of Iowa.