One evening last August, as Edward Kerry Sullivan stood outside his apartment building on Staten Island, a car pulled up and a man got out. By Mr. Sullivan’s recollection, the conversation went like this:

“Are you Edward Sullivan?” the man asked.

“That’s me,” Mr. Sullivan said.

“Do you have anything on you that I should be worried about?” the man asked.

“Who are you?” Mr. Sullivan replied.

“Police,” the man said. “You’re under arrest.”

A second police officer, in plain clothes like the first, stood by. They handcuffed him and then folded him into their unmarked car.

The officers told him, Mr. Sullivan said, that they had been watching him for several days.

The crime?

He had written “The Jerk,” about three inches high, on a campaign poster for James P. Molinaro, the Staten Island borough president. The undercover officers had taken a picture of the poster. There was no question that Mr. Sullivan had written it; moreover, there was no doubt that for weeks before that, he had launched far more pungent strikes against Mr. Molinaro in letters to a newspaper and public officials, criticizing the borough president’s plans to develop part of the Staten Island waterfront.