With the Iowa caucuses just three weeks away, a new poll shows Newt Gingrich continuing to lead the field for the Republican presidential nomination, but it suggests that there could be a few chinks in the Gingrich armor.

A University of Iowa Hawkeye Poll released Monday puts the former Speaker of the House at the top of the heap with 29.8 percent of likely Republican caucus-goers, compared to 20.3 percent of the respondents supporting Mitt Romney. Ron Paul placed third with 10.7 percent.

However Frederick Boehmke, associate professor of political science in the UI College of Liberal Arts and Sciences and faculty adviser of the Hawkeye Poll, says that although Gingrich is in the lead, he may be losing support.

"Gingrich's 29.8 percent share among likely GOP caucus-goers still gives him a nine-point lead over Romney, but our results show that his support may be starting to slide as it has with previous frontrunners," Boehmke says. "The gap has closed to 5.1 percentage points even though Romney's support has changed very little."

Perhaps more alarming for the Gingrich campaign, the poll shows that his lead over Romney is even smaller among "very likely" caucus-goers, with 29.0 percent stating they would vote for him if the caucuses were held today compared to 22.6 percent who identified Romney as their preferred candidate.

"Gingrich faces at least two obstacles according to our data," Boehmke says. "His run at the top may be starting to tail off as it has for previous front-runners. He also faces the challenge of turning out his supporters on caucus night, which will be critical since the gap between him and Romney is narrower among ‘very likely' GOP caucusers."

Among other candidates, Michelle Bachman had 8.5 percent, Rick Perry had 8.2 percent, Rick Santorum had 5.3 percent, Herman Cain had 4.4 percent, and Jon Huntsman had 1.5 percent.