Speaking to a crowd of 2,300 at West High School in Sioux City, Trump pleaded with the crowd for help.
"Will you get these numbers up?" Trump asked the crowd. "I promise you I will do such a good job. First of all, I am a great Christian –- and I am –- I am. Remember that. And I do well with the evangelicals. But the evangelicals left me down a little bit this last month. I don't know what I did. But I am a great Christian.
"Please do me a favor. Let me win Iowa," he also said.
Trump's comments come on the heels of 3 statewide polls showing Trump’s lead dropping in the Hawkeye state - the latest from Monmouth University shows Trump with 18 percent compared with retired neurosurgeon Ben Carson leading with 32 percent. A new CBS/New York Times national poll shows Trump's national lead completely gone, placing him in a neck-and–neck battle with Carson.
"What is my competition? Do you think these guys? I’m not going to say Carson. I’m not going to say [Marco] Rubio, who really is way down. I mean I am second, that's not like terrible. I don't like being second. Second is terrible to me," Trump said. "But do you think that Ben is going to go to China?"
Before taking questions from the audience, Trump also spoke critically of super Pacs -- even his own.
"It's a disgrace that we have them," he said as the audience cheered. "The money comes in. What do they do with the money? I don't know."
Still, Trump came back to his lagging poll numbers in the state repeatedly.
"Until Iowa came along, I said 'every poll' [had me in first place]. And then Iowa came -- What ... are you people doing to me?" he said.
In an unusual move for the candidate, he took questions, one of which from a wounded vet. Trump got off stage and talked for a bit with the veteran, who is unable to work and whose primary care giver is his wife. Trump vowed, as he has previously, to reform the Veterans Administration, to improve care for vets.
Trump heads to Colorado tonight ahead of the third Republican debate Wednesday night.