Democratic presidential candidates Dick Gephardt (search), Howard Dean (search) and John Kerry (search) were bunched at the top of a poll of the most likely voters in January's Iowa caucuses.

The poll, conducted for Planned Parenthood (search), showed Gephardt at 21 percent; the Missouri congressman won the Iowa caucuses in his unsuccessful 1988 White House bid. Dean, the former Vermont governor, was at 20 percent, and Massachusetts Sen. Kerry 18 percent.

The poll, released Wednesday, surveyed participants in the 2000 Iowa caucuses. Democratic pollster Paul Harstad has conducted surveys for Sen. Tom Harkin, D-Iowa, and Democratic Gov. Tom Vilsack.

Gephardt has led in other Iowa polls with Kerry in striking distance. Dean, who surprised many by raising $7.5 million in the second quarter of fund raising, has moved up among the leaders.

When Harstad surveyed voters who participated in the caucuses during the last two decades, Gephardt held a slight lead over Dean and Kerry. When focused on those most likely to take part next year, "the Iowa caucus is a virtual dead heat among Gephardt, Dean and Kerry," Harstad said.

Sen. Joe Lieberman (search) of Connecticut was at 11 percent; the remaining candidates were in single digits.

The poll of 611 caucus voters was conducted June 16-24, before the recent fund-raising numbers, and had an error margin of plus or minus 4 percentage points. The subgroup of 328 who participated in the 2000 caucuses had an error margin of plus or minus 5 percentage points.