Manchester, N.H. — Rick Santorum was minutes away, zooming down Interstate 293, but the fire marshal at Belmont Hall, a banquet center, was already nervous. “Let’s move,” he said, eyeing reporters and Occupy protesters. “Everybody, go to the parking lot, and quick.”

Diners in the adjacent restaurant nodded approvingly; burly cameramen groaned and toted their heavy bags outside. Santorum staffers, unprepared for the audible, hustled out the door with the lectern, and were greeted by a pack of college students holding homemade signs, mostly reading “Google Santorum” and “Legalize Marijuana.”

As the crowd swelled, a pickup truck pulled up, and Santorum was surrounded as he jumped out of the passenger’s seat. With his gray sweater vest and dark jacket, he looked like a math teacher who had stumbled into a Phish concert, surrounded by grungy students and hecklers who immediately pestered him with questions about gay marriage, drugs, and the “99 percent.”

“Why won’t you debate me?” asked Vermin Supreme, a left-wing activist and perennial presidential candidate. As Santorum shook hands, Vermin Supreme repeatedly screeched the challenge into his bullhorn. Santorum squinted and shook his head. “You mind if I meet some constituents?” he asked.

“Your constituents?” an onlooker asked, scowling.

“My potential constituents,” Santorum replied.

As he moved toward the lectern, the questions kept coming. “Is the gay-marriage issue hurting you here?” asked a reporter.

“I don’t think so,” Santorum replied. “We have a very strong record.”

The persistent Vermin Supreme followed. “Why won’t you marry me?” he yelled.

Santorum rolled his eyes. “Obviously you’re going to have protesters,” he said. And then he grinned. “We have a problem of having too many people coming to our events, and then having to bring them outside.”

Once Santorum had made his way across the asphalt, he clasped the lectern, looked down, and sighed. Because of the impromptu setup, there was no microphone. Vermin Supreme offered his bullhorn. Santorum narrowed his eyes as an audience member handed him the device, and kept his fingers far away from the mouthpiece. He set it on the table. “I don’t need it,” he said.

Watching the scene, a nearby journalist wondered: “Who advanced this event?”

A few minutes later, after Santorum had given his usual stump speech, focusing on his blue-collar roots and his plan to revive manufacturing, he opened the parking lot to questions. A group of college students with pro-marijuana signs hoisted one young man onto their shoulders; he stretched his hand into the air, desperate to be called on. “I certainly respect you putting up with all this,” one gentleman remarked to Santorum.

“What’s ‘this’?” Santorum asked. “Look, I come from southwestern Pennsylvania. I represented a district that had more steelworkers in it than any district in America.” He paused and glanced at the sign-wavers. “This is cake. When you’ve got steelworkers, that’s serious.”

But even Santorum, usually a placid, wonky presence, momentarily lost his politician’s poise as stragglers peppered him with questions and barbs. When more Occupy protesters arrived, however, he chuckled, amused at how his “town-hall meeting” had become a gathering place for angry progressives and local kooks. “This is a great venue; this is a slice of life,” he said. “This is like a Fellini movie.” The reference to the surrealistic Italian auteur drew laughs.

Yet the Manchester event, like many this week in New Hampshire, appears to have rattled Santorum and slowed his surge following the near-victory in the Iowa caucuses. After spending months in the Hawkeye State, where he was met at most stops by pensive evangelicals, he is no longer a fringe candidate. As happens with most poll leaders, however, the fringe now comes to him.