With just six months until the Iowa caucuses, businessman Donald Trump (17 percent) leads the field of Republicans among likely GOP caucus voters, according to a poll from Suffolk University.

Meanwhile, a subset of voters who watched the Aug. 6 Republican debate said that Sen. Marco Rubio (R-Fla.) and Dr. Ben Carson were the most impressive candidates.

The Suffolk University Iowa poll showed Gov. Scott Walker of neighboring Wisconsin second at 12 percent; Rubio, 10 percent; retired neurosurgeon Carson, 9 percent; and Sen. Ted Cruz (R-Texas) and businesswoman Carly Fiorina tied at 7 percent.

Former Florida Gov. Jeb Bush polled at 5 percent, followed by Ohio Gov. John Kasich (3 percent), while former Arkansas Gov. Mike Huckabee, Sen. Rand Paul (R-Ky.), and New Jersey Gov. Chris Christie were tied at 2 percent. Six other candidates received 1 percent or less, while 20 percent of voters were undecided.

“It appears that Donald Trump’s lead is strong so long as the number of active opponents remains above a dozen,” said David Paleologos, director of the Suffolk University Political Research Center in Boston. “If the Republican field were winnowed down to five or six candidates, Trump’s 17 percent probably wouldn’t be enough to win in Iowa, as polling indicates that his further growth has limitations. The long-shot candidates staying in the race help keep Trump on top—at least for now.”

Debate Impact

The race was closer among viewers of last Thursday’s debate: Trump and Walker were tied at 14 percent, with Rubio (11 percent), Carson and Fiorina (tied at 10 percent), and Cruz (9 percent) close behind. However, among likely caucus voters who skipped watching the FOX NEWS debate, Trump (21 percent) led Carson (10 percent) by a wider margin, with Rubio and Walker tied at 8 percent.

“In the absence of a debate, Trump’s lead widens because he swallows up the political oxygen, but when that oxygen is spread out more evenly in a debate, it breathes life into the other candidates, and the race gets closer,” said Paleologos.

When viewers were asked about Trump after seeing him debate, 55 percent said they were less comfortable with him as a candidate for president, and 23 percent said they were more comfortable. Forty-one percent said the debate moderators targeted Trump unfairly, while 54 percent disagreed.

Debate performance

Both Rubio and Carson benefited from strong debate performances and are within striking distance of the leaders. When debate viewers were asked which candidate was most impressive, Rubio led with 23 percent, followed by Carson with 22 percent. Carson and Rubio also topped the field at 12 percent each as viewers’ second choice—an indicator of future growth potential. When viewers shared in their own words which debate moment they remembered most, Carson dominated, with 25 percent mentioning his closing remarks, brain surgery comments, or providing other positive feedback.

Though she did not appear on the evening debate stage, Fiorina made her mark among afternoon debate viewers, 82 percent of whom said Fiorina was the most impressive of the seven candidates in the earlier debate. Among viewers of either debate, 93 percent said Fiorina should be invited to debate the top tier of Republican candidates in the future.

History of Suffolk Research in Iowa

In the most recent Iowa Republican primary for U.S. Senate, the April 2014 Suffolk University poll was the first to show then-State Sen. Joni Ernst overtaking front-runner Mark Jacobs. In May, Suffolk polled three bellwether counties—Black Hawk, Boone, and Washington—all of which indicated a landslide win for Ernst. She went on to defeat her four Republican opponents with a 38-point margin.

Methodology

The statewide survey of 500 likely Iowa presidential caucus voters was conducted Aug. 7-10, 2015, using live telephone interviews of Republican primary voter households where respondents indicated they were very or somewhat likely to attend their local caucuses for president in six months. The margin of error is +/-4.4 percent at a 95 percent level of confidence. Marginals and full cross-tabulation data are posted on the Suffolk University Political Research Center website. For more information, contact David Paleologos at 781-290-9310, [email protected].