Donald Trump is still soaring in Iowa - but there are now some clear warning signs
The Suffolk University survey found Trump leading the Hawkeye State with a relatively low plurality: 17% of the Republican vote.
Wisconsin Gov. Scott Walker (R) placed second at 12%, followed by US Sen. Marco Rubio (R-Florida) at 10%, and retired neurosurgeon Ben Carson at 9%.
But the poll also showed signs of limited potential growth for Trump after a debate performance that ended up creating more controversy.
"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.
"If the Republican field were winnowed down to five or six candidates, Trump's 17% 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."
Some of the warning signs for Trump:
- Contrary to his public proclamations, most Iowa voters don't think he "won" the debate. He came in fourth place when respondents were asked which candidate "impressed" them the most, behind Rubio, Carson, and Sen. Ted Cruz (R-Texas).
- Among respondents who watched the debate, Trump fell into an overall tie with Walker when voters were asked their first choice for the GOP nomination. His performance is much more impressive among voters who didn't tune in: He gets 21% of those voters, with Carson trailing behind at just 10%.
- Just 23% of Republican voters said they were "more comfortable" with Trump as a candidate after the debate, compared with 55% who said they were "less comfortable." And a majority - 54% - disagreed that the moderators "targeted Trump unfairly."
"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," Paleologos said.
Still, the poll was the second in Iowa and the fourth overall over the past three days to give Trump an overall lead, despite him subsequently going back and forth with Fox News host Megyn Kelly. A Public Policy Poll survey released on Monday found Trump leading Carson by 7 points, 19-12. And on Monday, the firm Morning Consult released a poll that showed Trump's support nationally increasing to 32% from 25% last week.
Another candidate hit in the poll was former Florida Gov. Jeb Bush (R), who is seventh in the state with about 4.6% of the Republican vote, behind risers like Cruz and former Hewlett Packard CEO Carly Fiorina, who many pundits and analysts said had the strongest performance of the early, lower-tier debate.
The survey of 500 likely Iowa Republican voters was conducted last Friday through Monday, and has a margin of error of plus-or-minus 4.4%.