By John Whitesides, Political Correspondent
DES MOINES, Iowa (Reuters) - Democratic presidential contender John Kerry opened a five-point lead on three tightly bunched rivals in Iowa three days before the state's caucuses, according to a Reuters/MSNBC/Zogby poll released on Friday.
In the latest three-day tracking poll, Kerry gained two percentage points to 24 percent, with Howard Dean and Richard Gephardt each dropping two points to 19 percent and John Edwards holding steady at 17 percent.
All four contenders were within the poll's margin of error of 4.5 percent, setting up a tight dash to the finish in Monday's caucuses, the first Democratic nominating contest.
"Any one of the four can win this one," pollster John Zogby said. With Iowa voters taking a final look at candidates and trying to make a choice, 13 percent of likely caucus-goers are still undecided.
The rolling poll of 503 likely caucus-goers was taken Tuesday through Thursday and will continue each day until Monday's caucuses.
Dean and Gephardt have battled back and forth for months for the top spot in polls in Iowa, but the late charges by Edwards and Kerry have scrambled the Democratic picture.
Kerry, the Massachusetts senator, leads among Democrats, young and old voters, men and women, liberals and moderates, and those who say they are "definitely" voting in Monday's caucuses, Zogby said.
"The issue will be, as it always is, turnout," Zogby said. "Gephardt has arguably the best team on the ground."
The polling was conducted as the leading candidates for the right to challenge President Bush in November exchanged an escalating series of attacks over their positions on the war in Iraq, trade, Medicare and Social Security.
Dean, the former Vermont governor, still holds a shrinking lead over retired Gen. Wesley Clark in polls in New Hampshire, which has a Jan. 27 primary one week after Iowa. Gephardt, the congressman from neighboring Missouri who won Iowa during his first presidential bid in 1988, needs to win to remain viable in the race.
For Edwards, who struggled late last year to get his campaign off the ground but has surged this month by refraining from attacking his opponents, even a third-place finish would be a tremendous boost.
Clark and Ohio Rep. Dennis Kucinich were at 3 percent, with Connecticut Sen. Joseph Lieberman at 1 percent and former civil rights activist Al Sharpton at less than 1 percent.
Clark and Lieberman are not competing in Iowa.
Polling in Iowa is complicated by the unique nature of the caucus system, which requires participants to leave their homes on a typically bitter cold night and gather with neighbors before publicly declaring their support for a candidate.