Sen. Bernie Sanders, I-Vt., doesn't seem all that thrilled at liberal megadonor Tom Steyer's decision to throw his hat in the ring for the 2020 presidential election.

"I like Tom personally," Sanders told MSNBC's Andrea Mitchell on Tuesday, while also lamenting the expanding wealth of America's "billionaire class". "But I do have to say as somebody who in this campaign has received two million campaign contributions, averaging I believe $19 a person, I am a bit tired of seeing billionaires trying to buy political power."

When Steyer announced his bid on Tuesday, he emphasized reducing corporate influence in politics. Touting his record “as an outsider,” Steyer noted that “I’ve led grassroots efforts that have taken on big corporations and won results for people. That’s not something you see a lot of from Washington these days. That’s why I’m running for President.”

But Sanders indicated that Steyer might raise red flags among Americans concerned about economic inequality.

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"I think the American people understand that one of the great problems facing American society today is that we have a billionaire class which is getting richer and richer while the working class of this country is struggling and in fact has been decimated over the last 45 years," Sanders told MSNBC.

Sanders went on to call for "public funding" of elections, pointing to how some people wanted the Supreme Court to overturn the Citizens United decision.

"People are sick and tired of big money in politics ... Billionaires -- and this is not just Tom Steyer -- billionaires should not be able to spend unlimited sums of money trying to buy elections," he said. Fellow progressive and 2020 hopeful, Sen. Elizabeth Warren D-Mass., seemed to also push back on Steyer's run, tweeting that the primary shouldn't be "decided by billionaires."

Steyer, a 62-year-old former hedge fund manager, has become a force in national politics. Five years ago he created NextGenAmerica, a grassroots advocacy organization that helped drive the youth vote in 2018, helping the Democrats win back the House of Representatives. And over the past two years, he’s become one of the ringleaders in the push to impeach Trump -- through his ‘Need to Impeach’ movement.

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His call for impeachment didn't sit very well with House Speaker Nancy Pelosi, D-Calif., who in July of 2018 said she wished her "friend" Steyer would instead focus his spending on opposing Trump's tax reform bill.

Fox News' Paul Steinhauser contributed to this report.