A source at the Democratic National Committee told CBS News that Chairman Terry McAuliffe talked with Clark a couple of nights ago and Clark said he was 90 percent ready to run.
He's also told friends he's leaning strongly toward entering the contest, he's contacted potential campaign advisers and asked for political advice from many party veterans. The 58-year-old former NATO commander could shake up the crowded field.
Clark is expected to announce his decision within a week.
Supporters say they've gotten pledges for more than $1 million if Clark enters. With just four months before the first votes are cast, though, Clark would be far behind some of the other candidates in organizing his campaign, raising money and building support in the early states. His earliest allies would be from former President Clinton's Arkansas-based political network.
"He's all potential and upside," said Democratic strategist Donna Brazile. "The question will be whether he could put together the organization so late."
Clark confirmed Thursday he has been putting a campaign plan together but chalked it up to the type of "parallel planning" common in the military. "If you want to find out whether you're going to go ahead, you have to have financial resources and you have to have staff available," he told The Associated Press.
While mulling his options, Clark has met with several presidential contenders who covet his endorsement and might consider him for a vice presidential slot. He met Saturday with former Vermont Gov. Howard Dean, who said it is too soon to talk about political alliances.
"There is a lot of vetting that would have to be done before you would have those kinds of discussions," Dean said when asked whether he had discussed the vice presidency with Clark.
If Clark were to enter the race, it would be to win the nomination and not simply position himself for the No. 2 slot, friends said.
Clark has a resume that unnerves potential rivals — Rhodes scholar, first in his 1966 class at West Point, White House fellow, head of the U.S. Southern Command and NATO commander during the 1999 campaign in Kosovo.
Dean's effort to solidify his front-runner status might suffer from the distraction of a Clark candidacy. Sen. John Kerry of Massachusetts would no longer be the race's only decorated combat veteran. Sens. John Edwards of North Carolina and Bob Graham of Florida would face another Southerner.
Senior party leaders say Clark or his advisers have contacted several prominent Democrats in the last few days about jobs in the campaign. Among them are Mark Fabiani, who ran Al Gore's communications team in the 2000 campaign.
If he enters the race, Clark would benefit from the support of a legion of Arkansas Democrats who helped Mr. Clinton get to the White House, including Skip Rutherford and Bruce Lindsey. Mr. Clinton has not taken sides in the nomination fight, but his glowing assessment of Clark in private talks has been noted by his oldest allies.
"There are a lot of people from Arkansas who will back Clark," said Bob Nash, who worked for Mr. Clinton in Arkansas and at the White House. "Part of it is he's our homeboy, and because he's an impressive man."
Clark also talked to John Weaver, a top strategist in the 2000 presidential campaign of Republican Sen. John McCain of Arizona, but Weaver is not joining the campaign because of health problems.
Clark believes his four-star military service would counter President Bush's political advantage as a wartime commander in chief, friends say. The retired general has been critical of the Iraq war and the administration's postwar efforts, positions that would put him alongside Dean, Graham and Rep. Dennis Kucinich of Ohio as the most vocal anti-war candidates.
Clark is scheduled to deliver a speech at the University of Iowa on Sept. 19, but is expected to make his decision before that, with an announcement likely in Little Rock, Ark.