Arlen Specter, comedian?

PHILADELPHIA - Knock, knock. Who's there? It's former Sen. Arlen Specter and he's continuing his second career as a comedian.

The longtime Pennsylvania senator performed at an open-mic night at the Helium Comedy Club in Philadelphia on Tuesday, continuing a post-politics foray into standup.

Specter told the crowd he's "been in comedy now for 30 years" and took shots at former Pennsylvania Gov. Ed Rendell, New Jersey Gov. Chris Christie and others in his act. Former President Bill Clinton and current Republican presidential candidate Newt Gingrich were also targets of Specter quips.

The Philadelphia Inquirer reports the crowd roared with approval at Specter's jokes. Specter himself tells the newspaper that "humor is elevating" and he wanted to try it out.

He says, "I might be invited back."