Republican presidential candidate Donald Trump admitted Tuesday that his decision to skip the final debate before Monday's Iowa caucuses could have cost him victory in the Hawkeye State. 

Despite leading in most of the pre-caucus polls, the real estate billionaire finished second behind Texas Sen. Ted Cruz and barely held off Florida Sen. Marco Rubio, who placed a close third. 

"That could've been with the debate," Trump told reporters at a rally in Milford, N.H. "I think some people were disappointed that I didn't go into the debate."

Trump declined to participate in the Jan. 28 Fox News/Google debate in Des Moines due to a dispute with Fox News Channel. He cited the tone of press statements from the network about his possible pulling out of the debate, as well as issues with one of the debate moderators, Megyn Kelly. 

Instead of participating in the debate, Trump held a fundraiser for veterans that raised $6 million. The candidate said Tuesday that he would make the same decision again, saying he "would never, ever give that up to go between first and second in Iowa."

Entrance polls conducted by Fox News showed that 55 percent of caucus-goers who made up their minds in the final few days chose to support Cruz or Rubio.

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Later Tuesday, Trump told Fox News' Sean Hannity that his campaign "didn't have much of a ground game because I didn't think I was going to be winning."

"In retrospect, we could have done much better with the ground game," Trump said, in an apparent slight to his Iowa state director Chuck Laudner.

Laudner had said in January he felt "fantastic about the ground game."

The Associated Press contributed to this report.