Overall, Trump polled at 24 percent among Republican voters in Iowa, followed by retired neurosurgeon Dr. Ben Carson at 17 percent, and former technology executive Carly Fiorina at 13 percent.
But when the Democratic-leaning PPP did head-to-head match-ups between Trump and other prominent GOP candidates, the real estate mogul found his only victory at 14 points over Bush.
Carson, Fiorina, Sen. Marco Rubio (FL), and the now-former candidate Wisconsin Gov. Scott Walker beat Trump by double digits. Carson took the biggest victory over Trump at 27 points.
Walker suspended his presidential campaign Monday and urged others to do the same: "I believe that I am being called to lead by helping to clear the field in this race so that a positive, conservative message can rise to the top of the field."
Some of Trump's off-the-cuff rhetoric does seem to be catching up with him. Fifty-nine percent think his comments on Fiorina's appearance were inappropriate as well as 49 percent who think his comments about Columba Bush were inappropriate.
The poll was conducted among 488 "usual Republican primary voters" from Sept. 18 to 20 with 80 percent completely the poll by landline. The margin of error was plus or minus 4.4 percent.