DES MOINES, Iowa — A late surge by Democratic presidential candidates John Kerry and John Edwards has pushed them slightly ahead of long-standing front-runners Howard Dean and Dick Gephardt in the race to win Monday's Iowa caucuses, a new Des Moines Register poll shows.

Kerry, a U.S. senator from Massachusetts, leads the Iowa poll with 26 percent of likely caucus participants naming him their first choice for the presidency. The poll, conducted Tuesday through Friday, also showed him gaining strength as the week wore on.

Edwards, a North Carolina senator who was in single digits in an Iowa poll taken two months ago, follows in second place at 23 percent — his highest finish in any media poll.

Dean, the candidate who seemed to be in the driver's seat as recently as two weeks ago with a key endorsement from Iowa Sen. Tom Harkin, has slipped to third at 20 percent. But the former Vermont governor remains within striking distance of the lead in an unusually close race in which almost half of caucusgoers say they could still change their minds.

Gephardt, the Missouri congressman who is counting on a strong finish with help from labor unions, has dropped to fourth place at 18 percent. Gephardt won the caucuses in 1988 before losing the nomination to Michael Dukakis.

"The character of the race has changed dramatically. Kerry has surged into the lead, followed by an even more spectacular move by Edwards into second place," said J. Ann Selzer, the Register's pollster.

"The luster has faded from Dean's campaign, and Gephardt has stumbled down the stretch as well," Selzer said.

Four other candidates trail far behind in single digits, led by U.S. Rep. Dennis Kucinich of Ohio at 3 percent. Kucinich has been actively campaigning in the state, but Wesley Clark, at 2 percent, and Joe Lieberman and Al Sharpton, at 1 percent each, are not competing in the caucuses.

The poll has a margin of error of 4 percentage points. Percentages include those who say they are leaning toward supporting a particular candidate.

It takes more than popularity to win the caucuses, however. Campaigns must get supporters to their meetings Monday and keep them on board while recruiting other candidates' supporters and undecided voters.

The quartet of candidates still in the thick of the race have two days left to sway opinions and urge supporters to attend the caucuses, which launch the presidential nominating process.

Candidates generally aim to finish third or better in Iowa to strengthen their bids in New Hampshire and other states with early nominating contests. Exceeding political pundits' expectations is also an important campaign goal.