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Pete Buttigieg is nipping at the heels of Bernie Sanders and Elizabeth Warren when it comes to campaign donations -- thanks, in no small part, to Mayor Pete's strong celebrity backing.

We combed through 2019 Federal Election Commission filings to find which celebs keep cutting checks for Pete, Bernie and Liz ... and Buttigieg has the upper hand.

Zachary Woods is right behind with his $2,500 donation ... and Pete got $1,500 from both Anthony Rapp and Emmy Rossum, plus $1,000 each from Ben Platt, George Takei and Christine Taylor.

Josh Holloway's wife, Yessica, chipped in $3,000 ... while Thomas Lennon contributed a little under $900, Cherry Jones and Meredith Baker added $200 and Harvey Fierstein gave $100.

All told, including non-celebrities, Mayor Pete's campaign raised north of $19 MILLION in the 3rd quarter, and only Sanders ($25.2 mil) and Warren ($24.6 mil) raked in more among Democrats.

The list isn't as long, but Sanders and Warren are getting some support in Hollywood. Bernie's includes $550 from Mark Ruffalo and $250 from Jason Mraz and Matthew McGorry ... plus $2,500 from Dan Castellaneta, the voice of Homer Simpson.

David Pierce is hedging his political bet, plopping another $2,800 down for Warren ... and she also got $1,000 from Lance Reddick, $500 from Rosie O'Donnell, $284 from Lily Tomlin, $250 from Chelsea Peretti and William Baldwin and $200 from Adam Arkin.