There was no Secret Service, no limousine, no blockaded streets. The official seal was nowhere in sight, nor were toadying aides. He crept in, in fact, after the show had begun, slipped silently into his front-row seat and, fingers steepled, watched the kids onstage, absorbed. This was like no president who ever came to Baltimore.

Well, to be technical, he's not a Commander-in-Chief: He's an actor who plays one on TV. But by any measure - Nielsens, Emmy Awards, critical raves - Martin Sheen's popularity ratings are high across the land. Sheen, who plays erudite President Josiah Bartlet on the NBC smash hit The West Wing, was in the city yesterday afternoon, his latest stop on what's become a political tour. He took in a rehearsal of the Youtheatre players - a troupe of African-American kids between 10 and 17 who take part in an after-school performance program.

Sure, Jed Bartlet had a glint of artificial L.A. auburn in his slicked-back hair. Sure, the jeans were studiedly casual. And yes, the real-life liberal activist had Democratic gubernatorial candidate Kathleen Kennedy Townsend, a longtime friend, in tow.

But there was one rock-solid sign he'd never make a true-to-life president: For more than half an hour, he sat quietly, soaking in the work of 30-odd fellow actors.

Under pink and blue gel lights, the kids spread across the stage. They sang two renditions of the spiritual "Hosannah, Forever, We Worship You." By the time Sheen arrived, one girl was engaged in a monologue of U.S. history, told through the eyes of the oppressed.

When she finished, 150 parents burst into applause. Sheen stood to clap, too.

Were those on stage overwhelmed by their guest's fame? Not really. Tevin Brown, 10, of Baltimore and Megan Exum, 15, of Columbia, admitted they'd never seen The West Wing. Julie McMillan, 15, of Baltimore City College, had seen Sheen only in Apocalypse Now. "I'll be sure and start watching now," she said.

For his part, the veteran actor treated the youngsters as peers. "I'm truly humbled at your talent and at the opportunity to be here," he told them. Learn your Shakespeare, he advised. Above all, stretch as an artist and "you'll defeat the only enemy you'll encounter - yourself."

The only ones who did seem dazzled by the faux president were the real-life pols. "I just met him in the parking lot an hour ago," said Len Foxwell, Townsend's press secretary. "He has that dignity, that gravity. It was just like meeting the president!"

Sheen seemed oblivious. "I love what I'm doing now more than anything I've ever done," he said as he signed autographs. "I've had such good fortune. And with it comes a responsibility to give back."