Trump was viewed as honest and trustworthy by 34 percent of respondents while 55 percent said he was not, with more than 10 percent not sure.

The Clinton campaign declined to comment.

In the Iowa U.S. Senate race, Suffolk found the same result as that NBC/Marist poll: Republican Sen. Chuck Grassley leading Democratic challenger Patty Judge 52 percent to 42 percent with 6 percent undecided.

Irrespective of their choice for president, by a 53 percent to 31 percent margin, Iowans said Clinton will win.

“In Iowa, there is a marked difference between what voters will do at the polls and what voters think others will do at the polls,” said David Paleologos, director of the Suffolk University Political Research Center in Boston.

The tight race reflects current party registration in Iowa — 33 percent Republican, 32 percent Democratic and 35 percent “no party,” he said.

“With party registration evenly split, so are the opinions of voters from the Hawkeye state,” Paleologos said.

Although the margin did not change in the four-way ballot test, Paleologos said the results suggest that Stein and Johnson could have an impact in Iowa.