Democratic bundler Robert Zimmerman was sitting in a conference room in the Great Neck office of his public relations and marketing firm a couple of weeks ago, musing over his quietly inexorable climb into the elite levels of New York and national politics over the past 20 or so years.

On the walls hung maps of Long Island, a pastel photo illustration of Bill Clinton and Al Gore, and a poster of J.F.K. with John Jr. Mr. Zimmerman, 53, is a member of the Democratic National Committee and also a superdelegate, and is one of Senator Hillary Clinton’s top fund-raisers in the country. Though he himself does not have the wealth of, say, other major Clinton finance people like banker Hassan Nemazee and venture capitalist Steven Rattner, he has proven to be incredibly successful at convincing other people with disposable income to support his candidate.

Extraordinarily, Mr. Zimmerman has managed to do all of this while staying, geographically, outside of the cutthroat Manhattan political fund-raising scene, even as he cultivated a motley assortment of socially prominent friends and associates within it. He is a regular guest on Lou Dobbs Tonight, where he is usually introduced as a Democratic strategist and Clinton supporter, and sits on the board of the American Museum of Natural History, in an ex officio post appointed by the City Council speaker.

And thus he has turned what at one time may have seemed like a quixotic quest for political influence into … well, political influence, direct from the once-Republican stronghold of Nassau County.

“This is such a funny place for me!” said Mr. Zimmerman. “It’s such a funny twist of events for me.”

He has smooth, tanned skin, bright blue eyes and carefully coiffed gray hair. On this day he was wearing a Long Island uniform of sorts: gold watch, black wool turtleneck, tan trousers. He looks directly into your eyes as he talks, and his speech is silky, dulcet. It’s hard, when speaking to Mr. Zimmerman, not to think you are the most important person in the room, or perhaps even the world. “It’s fun, actually, but it’s different. Way different. I speak to media around the country, but normally it’s about issues. It’s about advocating a point of view, it’s analysis, it’s on Congressional issues or events taking place. It’s about how current events affect society. I don’t have to talk about me!

“So, let’s talk,” he said.

MR. ZIMMERMAN SPENT his early years in Newton, Mass., and moved to Great Neck when he was 9 years old. His father is an accountant; his mother, a homemaker. “My brother and I weren’t expected to be politically active, but we were always expected to be involved,” Mr. Zimmerman said.

Mr. Zimmerman recalled his “coming of consciousness, if you will” in the 1960’s and 1970’s, when politicians and public figures like Eugene McCarthy, Barry Goldwater and Jane Fonda would come to speak at his synagogue in Great Neck. “Especially in the 1970’s, we really felt like our voices mattered and we were part of a great dream, a great cause,” he said. “Whether it was fighting a corrupt cause overseas or working to impeach a president, or environmental issues, or workforce housing—it was a real sense of empowerment that your lives mattered and that you could have an impact on your society and be part of a larger picture. In many communities, homecoming was the big event or the high-school carnival. In Great Neck, it was the Saturday protest march in front of the post office or the community demonstration.” (Protest marches in Great Neck certainly do seem like they came from a different era.)

Today, Mr. Zimmerman takes a similar tack; his firm does not do political consulting. He tried running for Congress in 1982 and for State Assembly in 1986 and 1988. Since then, though, Mr. Zimmerman has preferred to remain in the background.

Now, he has the ear of Democratic leaders at the city level all the way up to Mrs. Clinton. “Robert is a true friend and a real believer who will always tell you what he really thinks,” Mrs. Clinton told The Observer through a campaign spokesperson. “I value support, and more importantly I value his honest input and advice.”

And he is extraordinarily valuable as a fund-raiser. “You have a group of us in New York referred to as the usual suspects,” said Mr. Nemazee, who is national finance chair for Mrs. Clinton’s campaign. “You have the Upper East Side, the Upper West Side and the downtown folks. Everyone knows everyone else. You socialize together, you do business together. I don’t want to say you’re fishing in each other’s ponds with donors, but a lot of people know a lot of the same people. When you’re dealing with someone like Robert, who knows a lot of people but not in the same geographical location, who’s reaching out to people you wouldn’t be reaching out to, it’s a huge plus.”

To raise money for Mrs. Clinton, in March 2007, Mr. Zimmerman co-hosted a dinner headlined by President Clinton; in August, he co-hosted cocktails at the Southampton home of prominent Democratic fund-raiser Bernard Schwartz; and in December, he held a “low-dollar” event at Hofstra University. “Sometimes you have certain donors who speak to the press who are not necessarily ‘on message,’” said Mr. Nemazee. “Robert is not only on message, but finds he is often the one suggesting the message.”

AFTER GRADUATING FROM Brandeis in 1976, Mr. Zimmerman briefly worked for former Congressman Lester Wolff and dropped out of law school at Hofstra after one year, finally getting an M.B.A. from Fordham in 1981. He has spent almost his entire life in Great Neck, about half an hour on the Long Island Rail Road from Penn Station, except when he has been at his weekend and summer home in Southampton, which he purchased eight years ago. (“That’s a very special place to me,” Mr. Zimmerman told me.)

He lives alone in an apartment, and the office of Zimmerman/Edelson Inc. is across the street from the train station; he and his business partner, Ron Edelson, employ 26 people, mostly 20-somethings who looked bemused as Mr. Zimmerman paraded me around the office. He has never been married and has no children, and it’s not hard to think of his political involvement as, in some way, his avocation and his extended family.

Soon we decamped for lunch at Bruce’s Bakery, a deli down the street from his office that could have emerged, intact, from an MGM lot. As soon as we walked in, a couple at a table by the entrance beamed and greeted him. But then: “Hey, all you need now is a photo of Obama with a spear, huh?” the man guffawed. This was a day or so after someone from the Clinton campaign had allegedly sent a photo of Barack Obama clad in traditional Somali garb to the Drudge Report.

Mr. Zimmerman looked horrified. “That’s inappropriate,” he said to the man, as we took our seats. “That’s just inappropriate.” He was briefly shaken, then recovered. “I’m terribly sorry about that—he’s just a man who lives in my building, and …”

I asked what he would have done, if he had been hired as a crisis consultant by the campaign in the aftermath of the photo. He brightened. “I think there are certain things that have to be done from the Clinton perspective,” he said. Back on message! “They have to be very clear in their denial and refocus on the issues that really matter.”

On March 5, the day after Mrs. Clinton revived her candidacy with wins in Texas, Ohio and Rhode Island, Mr. Zimmerman stayed resolutely on message in a late-evening phone conversation with The Observer. “One of the great aspects of this season is the fact that the voters have trumped the pundits and the pollsters every time,” he said. “I guess since I’m part of that pundocracy, if you will, as a Lou Dobbs contributor, I do love the fact that the voters have not been swayed by the predictions of the mainstream media. They haven’t been overwhelmed by the issues of who has the money. They’ve made very tough, independent analysis. The conventional wisdom has been wrong every step in this process, and I think that just great. I think the independence of the voter and their independent analysis has been just terrific.”

Then, in an almost exact parroting of Mrs. Clinton’s words to her Ohio supporters on the evening of March 4, he said, “Everyone who ever felt like an underdog or counted out could feel a sense of vindication at the way [Mrs. Clinton] took on the odds and won.”

Sometimes, Mr. Zimmerman makes news. On the evening of March 10, he appeared once again on Mr. Dobbs’ CNN show. On a day when most prominent Democrats hedged when asked whether Eliot Spitzer should stay in office despite his prostitution-ring allegations, Mr. Zimmerman stated unequivocally, “If the facts are as they appear, no, I don’t.”

But even this was less a spontaneous outburst than a calculated attempt by a partisan official to contain one official’s radioactivity before it spread.

Mr. Zimmerman’s success as a fund-raiser and surrogate is directly related to his ability to speak precisely. (No Samantha Power-type slip-ups here!)

His first attempts at raising money came during Al Gore’s first presidential campaign, in 1987. “I was collecting $50 checks and $100 checks, and that was hard to do,” he said. “I saw an opportunity. I was getting in my car and driving around to diners to talk to people, and knocking on doors.” The next year, Mr. Zimmerman founded his PR firm, and in 1990, he and Mr. Edelson formed Zimmerman/Edelson.

Since then, he has also accumulated a rather mind-boggling list of powerful New York friends, all of whom were eager to testify to Mr. Zimmerman’s loyalty and affability. Mr. Zimmerman, nearly everyone agrees, is just a nice guy.

“He’s an extremely personable, likable individual,” said the New York Post gossip columnist Cindy Adams, who met him at a birthday party Ms. Adams gave for the Broadway and film producer Marty Richards. (“It was Marty’s guest list, and Robert was there,” Ms. Adams explained.) “He goes out of his way for everyone. Whoever needs a favor, he’s doing it.”

“He’s beloved by many people,” said Tina Brown.

“Robert is one of those people who, when he is in a room, you know he is in a room,” said City Council Speaker Christine Quinn. “In a very, very good way!”

“He’s a great guy. He’s a great adviser,” said Representative Gary Ackerman, who represents Mr. Zimmerman’s district.

“I think it’s a simple thing,” said Nassau County Democratic Chairman Jay Jacobs. “He’s likable.”

Ask Mr. Zimmerman, though, and the answer is usually vague. This one, he met in the Hamptons; that one, at a dinner. “Then we just became friends” or “just over the years” are common refrains. He admittedly has no trouble simply going up to people and starting to talk to them, and so it’s not surprising that his list of friendly associates also includes such varied figures as New York Post editor Col Allen; New York Senator Chuck Schumer; writer Jay McInerney and his wife, the socialite Anne Hearst; The View co-host Joy Behar; Lou Dobbs; James Lipton, host of Inside the Actor’s Studio; former NYPD Chief William Bratton and his wife, TruTV analyst Rikki Klieman; and radio host Joan Hamburg.

Over the course of my reporting this article, Mr. Zimmerman often called me several times a day (or night)—sometimes just to check in, sometimes to see if I had managed to reach his various contacts, sometimes to offer up yet more friends to be interviewed. “It’s like I’m your stringer!” he said at one point.

There’s this story one of his friends likes to tell about the time he was walking by the Ralph Lauren store in the Hamptons and saw a leather jacket in the window, and even though it was August and not exactly the season for a leather jacket, he decided to try it on anyway, and as he was looking at himself in the mirror, someone came up behind him and adjusted the shoulders. “Absolutely perfect,” this person said, and wouldn’t you know, it turned out to be Ralph Lauren himself, and so Mr. Zimmerman purchased this very expensive jacket, and when his friend asked why he had bought the jacket, Mr. Zimmerman said, “I got a good story out of it.”