In the clip, Bloomberg, who shot a scene for Damon's upcoming movie "The Adjustment Bureau" on Tuesday, meets Damon by the waterfront to ask the actor to endorse his mayoral run because "people care about what [he] thinks," which is arguable.
Damon -- who, like Bloomberg, is famously from Boston -- acts skeptical and asks, "Do you focus-group this stuff?"
"There are a lot of people who say that a star like you, with experience like you, somebody who is part of new york and gets it and makes movies here..." Bloomberg pleads.
Damon claims he loves the job the mayor does and the "progress" he has made, but says he will only do the endorsement if it's something "original."
Cut to a scene of a very stiff-looking Damon, now in a boring Navy blue suit, giving a very dry and forced reading as he says "I'm Matt Damon and I highly endorse Mike Bloomberg for mayor of New York City."
Democratic rival William Thompson responded by noting that Damon isn't a real New Yorker.
"While the Mayor is busy courting endorsements from out of state celebrities, the unemployment rate in the City just hit 10.3 percent. Unfortunately for him, people who actually live in New York will decide this election," the Thompson campaign said in a statement.
Watch the video here: