DES MOINES, Iowa — Mitt Romney has regained the lead among Republicans in the race to win Iowa's GOP presidential caucus on Thursday, as Mike Huckabee has lost momentum and support, even among the evangelical Christians who had propelled him into the top spot just weeks ago.

At the same time, John Edwards has clawed his way into contention in the Democratic Party caucus, gaining strength even as his rivals for the presidential nomination, Hillary Clinton and Barack Obama have lost ground, according to a new McClatchy-MSNBC poll.

Taken together, this first poll in Iowa since campaigning resumed after a Christmas break showed a dead-heat contest between the three leading Democratic candidates and a volatile clash between the two top Republican rivals here.

"On the Democratic side, the race is about as close as it can get, but keep an eye on Edwards," said Brad Coker of Mason-Dixon Polling & Research, which conducted the survey of 400 likely Democratic caucus attendees and 400 likely Republican caucus attendees in Iowa was conducted by telephone from Dec. 26-28. "Edwards has really moved up since our last poll. Obama and Clinton have each slipped a little bit."

The new survey, taken Dec. 26-28, came three weeks after the initial Dec. 3-6 poll.

On the Republican side, Coker said, "Romney has rebounded and the Huckabee bubble may have burst.

"Last time, Huckabee was getting all the good press and nobody had put him under any scrutiny.... Now he's under the spotlight, and he's started to wilt a little."

Among Republicans:

—Former Massachusetts Gov. Romney has 27 percent
—Former Arkansas Gov. Huckabee has 23 percent
—Former Tennessee Sen. Fred Thompson has 14 percent
—Sen. John McCain of Arizona has 13 percent
—Former New York Mayor Rudy Giuliani has 5 percent
—Rep. Ron Paul of Texas has 5 percent
—Rep. Duncan Hunter of California has 1 percent
—Undecided: 12 percent

One in three Iowa Republicans say they could still change their minds.

No one knows that better than Huckabee, who surged into the lead three weeks ago and now has lost it just as quickly. Huckabee's support dropped 8 percentage points since the last McClatchy/MSNBC poll Dec. 3-6.

A major reason why is that he's come under sharp criticism from rivals such as Romney, been blistered as a tax raiser in a $500,000 ad campaign aired by the anti-tax group Club For Growth, and faced new scrutiny by the media of his Arkansas record on such issues as pardons.

He still ranks tops among Iowa Republicans who rank values and family issues their top concerns.