Tall, fair-haired, and patrician, strongly emitting that ineffable thing called presence, Timothy Rub is wandering through the galleries of the Philadelphia Museum of Art late one recent night like a kid let loose in a candy shop.

"Isn't that fantastic?" he says, sidling up to Monet's Water Lilies, Japanese Footbridge. "This is a superb painting." He points out the unusual thickness of paint and the diffuse ochres, tans, and greens that make the piece seem almost more abstract than impressionist.

Later, an early Tanguy steals his attention, then a pair of Warhols, then a burlap canvas of dense grids. "Isn't that a painting by Torres-Garcia?" he says.

Perhaps it is more accurate to say that Rub is like a kid who has just been given the candy shop. Lured from the Cleveland Museum of Art, he arrives in Philadelphia this fall to succeed the late Anne d'Harnoncourt as director and chief executive officer of the Art Museum - a move many art leaders view as a bit of inevitable justice.

"Tim is terrific. He has done a great deal for the Cleveland Museum. But Cleveland's loss is Philadelphia's gain," Museum of Modern Art president emerita Agnes Gund, who has ties to both museums, said through an intermediary. "Few people can step into Anne d'Harnoncourt's shoes and possess the same elegance and class and knowledge to position a museum. But Tim is such an individual."

Art Museum curators say Rub's arrival comes not a moment too soon. The museum has had temporary leadership since d'Harnoncourt's death in June 2008, and though planning for a $500 million expansion and other ambitions have continued, key decisions await an authority figure.

This is the perfect time, several say, to have an outsider - soon to be an insider - review plans by Frank Gehry's firm to expand and reorder the museum experience.

"He sounds like a smart guy, and it's always an advantage to have a fresh eye take a look at what you've planned, even if it only confirms your plans," says Marsha Perelman, a prominent Philadelphia contemporary-art collector and former Hirshhorn Museum and Sculpture Garden board member.

Observers sensitive to careerism view his departure from the Cleveland Museum of Art after only three years rather skeptically. Will he leave Philadelphia just as easily if, say, the directorship of the Metropolitan Museum of Art comes open?

Rub, 57, says no, Philadelphia is his destination: "There is no other place I would like to be." His reason for leaving Cleveland, midway through a $350 million expansion begun before he arrived, is not mysterious.

It's the art.

"I think it's a well-understood decision given the obvious distinction of this museum," says Evan Hopkins Turner, a Philadelphian who has led both institutions - Philadelphia's from 1964 to 1978, Cleveland's from 1983 to 1993.

"He made no secret about the fact that Philadelphia is a favorite of his," says Michael Horvitz, the Cleveland museum's board chairman. "The opportunity for him to be the leader of the museum that he has admired since he was a child, which I believe was really the foundation of his introduction to art history, it's an opportunity for him he couldn't pass up."

Rub wasn't a child when he began regular pilgrimages to the Philadelphia museum, but he was certainly in the infancy of his art education.

In the early '70s, Rub, a motorcyclist (owner of a Honda 450) with hair nearly to his shoulders, was an English major at Middlebury College. Obliged to take a course outside his field, he signed up for 20th-century art.

Rub was one of those students who have a formidable intellect but don't always apply themselves, a professor recalled.

"In order to encourage him to do more art history and maybe a little less partying, I gave him a key to my office and told him he was free to use it any time I wasn't in it," says John Hunisak, professor of history of art and architecture. "I knew I had a star on my hands, no question, and when he put his mind to working - which he had to be prodded to do sometimes - he was extraordinary in terms of what he produced."

Rub the museum director presents a highly refined veneer, but the impression in those days, Hunisak says, was of "a wonderfully individualistic character. His humor is so quirky, and he can mask it totally, which is terrific. But I think it's always there."

Growing up, Rub had no idea what his career might be. Born in Queens on March 9, 1952, and raised there (in Richmond Hill) until he was 7 and then in Westfield, N.J., he received early training as a violinist. His father was a banker, but also an active organist.

Rub studied violin from second grade until well into college, and went as far as attending the summer program at Interlochen, the highly respected arts camp in Michigan. "That proved to me how talented some people are. I was good," he says, but he didn't have what great violinists have. "They have something, like artists, remarkable in their fingertips."