He decided to run last month and received the nomination late last week. He now has to get at least 7,500 signatures to get on the ballot in November.

“When the Green Party approached him, he was thinking that Bloomberg was essentially purchasing a third term,” said Michael O’Neil, 29, the campaign’s press officer. “He wanted to run because it seemed unlikely that any of the front-runners in the election would speak to the issues that have been challenging New York City’s neighborhoods.”

Reverend Billy, who according to Mr. O’Neil makes a living with paid appearances at colleges and other venues, said refocusing attention on the city’s neighborhoods  he used the word “neighborhood” dozens of times  would be the centerpiece of his campaign, though he said little about other issues, like subway fares and the economic crisis.

He did make it clear that he did not approve of Mr. Bloomberg’s pursuit of a third term. “We’re at a critical point in the city’s history right now,” he said. “The mayor’s trying to privatize Union Square. We’re surrounded by logos everywhere. We need to oppose that.”

Reverend Billy, who grew up in the Midwest and arrived in New York from San Francisco in 1994, has long been known for his colorful street-theater tirades on what he sees as corporate intrusions on American life. He was arrested during a protest in Union Square in 2007 and that year was the subject of the documentary “What Would Jesus Buy?”