A new InsiderAdvantage/Majority Opinion poll out of Iowa shows John Edwards leaping from third to first place in Iowa, and the GOP field ever-tightening, as the Jan. 3 caucuses approach.

The Democratic poll, taken from Dec. 16-17 of 977 Democrats who said they intend to participate in the caucuses, showed Edwards with 30 percent, followed by New York Sen. Hillary Clinton with 26 percent and Illinois Sen. Barack Obama with 24 percent.

Click here to see the InsiderAdvantage poll.

The poll, which is an automated survey taken overnight, suggests the former North Carolina senator - who has been steadily trumpeting his anti-special interest, populist message - is resonating in Iowa. Other recent polls showed Obama overtaking Clinton, and Edwards stuck in third.

However, when the InsiderAdvantage poll's sample group was narrowed to 633 Democrats most likely to caucus, Obama retained a 1-point lead. That poll gave Obama 27 percent, Edwards 26 percent and Clinton 24 percent. The tighter sample group had a margin of error of 3 percent, while the broader group had a margin of error of 2 percent.

On the Republican side, the broader poll of 835 voters who intend to caucus showed former Arkansas Gov. Mike Huckabee with 28 percent, followed by former Massachusetts Gov. Mitt Romney with 25 percent. When the screen was tightened to 418 likely caucus-goers, the race flipped: Romney took 28 percent and Huckabee took 25 percent. The poll is a reversal from recent surveys showing Huckabee leading Romney by double digits.

The tighter sample group had a margin of error of 5 percent, while the broader group had a margin of error of 3 percent.