THE “Fire David Letterman” rally, held yesterday across the street from Letterman’s “Late Show” studios on Broadway and 52nd, attracted about 50 people.

John Ziegler, the group’s spokesman, acknowledged that it’s unlikely Letterman will be fired for joking on last week’s “Late Show” about Gov. Sarah Palin’s daughter getting “knocked up” by Alex Rodriguez during a visit to Yankee Stadium.

“My personal suggestion, if he’s really sincere, is why not give the salary he made off of last week’s shows to some charity he and Gov. Palin can agree on,” Ziegler told The Post. “I think that would be the absolute bare-bones minimum of accountability.”

Letterman has apologized twice for the joke, including an on-air meaculpa Monday night.

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