ARLINGTON, Va. -- Harold never forgets a favor, especially if he's the one who did the favor. So the veteran political operative made sure that, when the time was right, he alone would call Garry Shay, the former chairman of the Los Angeles County Democratic Party. As Mr. Ickes saw it, he had helped Mr. Shay; now he was looking for Mr. Shay to help him.

And once Mr. Ickes started calling, he didn't stop until Mr. Shay said the words Mr. Ickes wanted to hear -- that he would support Sen. Hillary Rodham Clinton of New York at the Democratic National Convention in Denver in August.

Mr. Shay, as a member of the Democratic National Committee, is a so-called "superdelegate," one of nearly 800 elected officials, party leaders and activists who -- with the state primaries and caucuses now expected to end in stalemate -- might effectively end up picking the 2008 Democratic presidential candidate.

And the man in charge of Clinton's effort to lock up superdelegates is Mr. Ickes, whose enthusiasm for no-holds-barred politics sometimes rattles friends and foes alike. Mr. Ickes once got so carried away that he bit another political operative on the leg. Now, some 35 years later, at age 68, he's mellowed so little it could happen again.

"It depends on how heated the circumstances are," he says.

Aggressive, profane, openly scornful of rivals, Mr. Ickes rules Clinton's superdelegate operation with an intimidating style and a mythic persona. He is "adviser, consigliere, enforcer and strategist" rolled into one, says Dick Harpootlian, a former chair of the South Carolina Democratic Party who backs Sen. Barack Obama.

Mr. Ickes comes by his temperament and his passion for politics naturally. He is the son and namesake of President Franklin D. Roosevelt's famously irascible Interior secretary. And he's played the role of party maverick for decades.

He worked in Sen. Eugene McCarthy's 1968 campaign to unseat incumbent President Johnson. He joined Sen. Edward Kennedy in trying to deny President Carter renomination's in 1980. He worked for Jesse Jackson's presidential bids in 1984 and 1988.

Unhappy about the way Mr. Jackson was being treated at the '88 convention, Mr. Ickes hatched plans that included a threat to hand out 1,700 plastic whistles to Jackson supporters so they could disrupt the proceedings.

Even inside the Clinton court, Mr. Ickes does not hold back. Last year, when senior Clinton aide Mark Penn appeared not to grasp the basics of delegate selection, Mr. Ickes mockingly asked, "Could it be that the vaunted 'chief strategist' of the vaunted Hillary Clinton campaign does not understand?"

In a Clinton campaign that can seem machine-like, Mr. Ickes is conspicuous for his idiosyncrasies. When a female aide noticed his dress shirt unbuttoned practically to the navel, she said it was like glimpsing an unzipped fly.

Temperament and eccentricities aside, with the importance of the superdelegates increasing, Mr. Ickes now carries a burden that might be second only to the candidate's own. Clinton is ahead among superdelegates, but the margin has been slipping. In December, she led Mr. Obama by 106 superdelegates. In early February, the number was down to 87. Today, it is 30, according to Associated Press surveys.

Mr. Ickes runs the superdelegate operation from a war room in this suburb across the Potomac River from the capital.

In courting the uncommitted, "the first order of business" is finding out "who is this person," Mr. Ickes said recently over an omelet. "What is his or her political history? Who does that person associate with or rely on for information they take into account when making political decisions?"

To get answers, aides sit at computers ranged along a windowless hallway outside Mr. Ickes' office. They sift Web sites, do Google searches, talk to friends, lobbyists, campaign donors -- tapping into what Mr. Ickes calls the network of "Clinton alumni."

"You establish a relationship and keep going back and people become friendlier and let down their guard," Mr. Ickes said, describing the campaign's methods. "And before you know it, you can pick up useful information. None of this is insidious information; it's information about what makes a person tick politically."

In the case of Mr. Shay, Mr. Ickes remembered that Mr. Shay had wanted to increase the representation of gays and lesbians within the national party. Mr. Ickes helped him over the years, speaking out in favor of Mr. Shay's project at DNC meetings.

Initially, Mr. Shay committed to former North Carolina Sen. John Edwards, so Mr. Ickes issued a standing order to his staff: Make sure that when Mr. Edwards dropped out, Mr. Ickes -- and only Mr. Ickes -- called Mr. Shay. Indeed, as Edwards' fortunes sagged, Mr. Ickes began calling to chat up Mr. Shay.

And Jan. 30, just before Mr. Edwards publicly quit the race, Mr. Ickes pounced.

"Look, personal relationships, especially when you're dealing with this at the individual level, are sometimes very helpful," Mr. Ickes said later. "I have no reservations about calling in a chit. I don't know if I had a chit with him to call in, but I do think that our prior relationship and the fact that I was helpful may have been helpful in persuading him to be for Hillary."

For his part, Mr. Shay insists that several factors played into his decision, including that he liked Mrs. Clinton's performance in the Los Angeles debate and that Mr. Obama never called him. But he credits Mr. Ickes with keeping Mrs. Clinton "within the forefront of my mind," and in fact he committed to her soon after Mr. Ickes placed the critical call.

Only months ago, most people gave little thought to the superdelegates. Mrs. Clinton seemed invincible. And for Democrats at least, the idea of uncommitted delegates picking the nominee evoked images of political bosses in smoke-filled rooms. Returning to that era was inconceivable.

Mr. Ickes recognized early how important those delegates might be. And, in assigning him responsibility for them, Mrs. Clinton chose a veteran whose loyalty was proven -- and whose iron focus on the goal at hand matched her own.

Both the loyalty and the focus were on display in February 1999 when the Senate voted not to remove Bill Clinton from office.

In the White House residence, Mr. Ickes and the first lady were poring over New York state maps in preparation for her Senate bid.

A call came in informing the first lady that her husband had been acquitted, Mr. Ickes recalled. "She puts down the phone and says, 'Harold, we were talking about Buffalo.' "

With that, they went back to work.