David L. Cohen has a habit of adding hats to his civic haberdashery.

Already a power player with Comcast, the University of Pennsylvania, the Chamber of Commerce, the Jewish Federation, the United Way, the Urban League, the American Red Cross, and the Democratic Party, Cohen is taking on more.

Beginning in November, he'll chair Penn's board of trustees - its first Philadelphia-based chairman since 1986, the university announced Wednesday. A Penn law school alumnus, Cohen joined the board in 2001.

"I admit to having trouble saying no, especially to good causes," he says. "There's a lot of need out there. I feel a personal and societal obligation to give back as much as possible."

Penn holds a special place for Cohen, whose wife, Rhonda, also graduated from the law school. He labels the university his "No. 1 passion, other than my family and my job," because, in part, it fuels his commitment to urban renewal and public policy.

Like the rest of the planet, Penn has been hit hard by the plummeting economy and needs Cohen's prodigious fund-raising skills. A dinner party at his Mount Airy home in October for Democrat Barack Obama notched $6.1 million, a state record.

The same month, as new chairman of the Greater Philadelphia Chamber of Commerce, Cohen pledged to lobby Harrisburg for more education funding as a way to make the region more competitive.

At the same time, he's fighting battles in Washington for Comcast - at a salary of $1.3 million, plus stock. His chief opponent is Federal Communications Commission chairman Kevin Martin, a Republican. Whether Cohen will have more juice with the new administration is unclear.

Cohen isn't sure how he'll squeeze his newest unpaid post into a standing-room-only schedule, but he says: "I will make time for Penn, as I always have and I always will."

In-demand dynamo

A preternatural multitasker, Cohen has more balls in the air than a professional juggler. He keeps them there due to his efficiency and organization, and by having more natural energy than someone half his 53 years.

"My day has a way of expanding to enable me to do the things I need to do," he says. "I'm pretty close to critical mass all the time."

Mark Schweiker, the Chamber of Commerce's president and chief executive officer and a recipient of Cohen's infamous 5 a.m. e-mails, describes Cohen's horsepower as "absolutely remarkable."

Cohen says his BlackBerry includes 3,503 names. He's booked into 2010, says his Comcast assistant, Jennifer Paternostro. At any time, up to 20 people are waiting for an appointment.

"Just looking at one week is enough to scare you," says Paternostro, 45, who began with Cohen nine years ago when he was chairman of heavyweight law firm Ballard, Spahr, Andrews & Ingersoll L.L.P.

'David never stops'

Hers is a 24/7 job, but at least it's never boring, she says. "Every time you turn around, he's on another board or he's got another job. David never stops."

When Cohen served as Mayor Ed Rendell's chief of staff from 1992-97, "the conventional theory was that there were actually two clones of me," Cohen says. "That way, we could show up at different meetings at the same time."

Cohen's energy cannot be fully explained, says Alan Kessler, a fellow Democratic rainmaker and big-time Philadelphia lawyer. "There's no question that somebody ought to check the DNA there."

Rhonda Cohen sees so little of her in-demand husband that she says: "We've been married for 30 years, but in terms of time, we're still on our honeymoon."

A few years ago, an exasperated Mrs. Cohen told Mr. Cohen that he had to learn to say no. To prove otherwise, he had Paternostro list all the invitations he had declined that month.

It was six pages, single-spaced.

'Still a friend' of Fumo's

"I still felt like he was saying yes to too many things," says Rhonda Cohen, 54, a former partner at Ballard Spahr, now retired. "At least he wasn't saying yes to

everything

."

Cohen insists he turns down "hundreds of things. There isn't a nonprofit organization in this community that hasn't asked me to be on the board. I don't believe in saying yes for the sake of saying yes."

Cohen's board membership at the Independence Seaport Museum came up at the ongoing corruption trial of former State Sen. Vincent J. Fumo, a friend.

According to testimony, Cohen sailed with Fumo, a board member, in 1998 on a yacht the museum owned. The government says the cruise is evidence of Fumo's misuse of the institution's property.

Fumo's lawyer says that his client used the yacht to interest powerful friends in the museum, and that afterward Cohen joined the board.

Cohen says Fumo "is still a friend, but not the same kind of friend" he was before Fumo's second divorce, in 2000. Their families used to vacation together.

Unlike her husband, Rhonda Cohen knew how to say no when she and David met as Swarthmore students. Absorbed with her job as editor of the school newspaper, she didn't want to date anyone. Including reporter Cohen.

"He thought I was playing hard to get because I kept saying no," she says. In those days, "he slept half the day, often through lunch. The compulsiveness didn't kick in until law school."

The couple has two sons: Josh, 19, a freshman at Emory University, and Ben, 23, a junior at Rider.

Though he labels himself "a great relaxer" who can instantly zone out with a book, Cohen says he'll never retire.

"My idea of hell is sitting at my desk with nothing to do. I can't imagine not being productive at all times."

Philadelphia hopes he stays that way.

Contact staff writer Gail Shister at 215-854-5626 or gshister@phillynews.com. Read her recent work at http://go.philly.com/gailshister