Tom Steyer, a top Democratic donor, said Pete Buttigieg, the former mayor of South Bend, Indiana, is the "real deal" and could go far in the 2020 presidential race.

Steyer, a staunch critic of President Donald Trump, also said he's impressed by Washington state Governor Jay Inslee's campaign and its focus on climate change.

The billionaire philanthropist told INSIDER it's a bit too early to endorse anyone, however, and he's going to wait and see.

One of the top five donors to Democrats in the US says that Mayor Pete Buttigieg is the "real deal" and there's no question he's a "serious" contender for the 2020 Democratic nomination.

Tom Steyer, a billionaire and philanthropist, told INSIDER, it's a "little preliminary" to say who can beat President Donald Trump in the general election given there's already a broad field of Democratic candidates that continues to grow. But Steyer pointed to Buttigieg, the mayor of South Bend, Indiana, as someone who's going to be in it for the "long run."

"What I'm looking for is somebody with a positive vision to explain to the American people what we're trying to do together. What it means to be an American, and what our relationship is with each other and with the government," Steyer said in a phone call on Thursday.

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Steyer said 2020 should be a "framing election where we recast, for the 21st century, how we're thinking about things" because the country is at a place of "intellectual and moral bankruptcy."

When asked if Buttigieg might be the person to bring the US into a new era or if the former mayor's surge in popularity is a passing fad, Steyer said, "He's the real deal. I don't think there's any question that he's serious and that he's going to be in this for the long run."

Steyer added that he's still familiarizing himself with what Buttigieg is "representing" and not in a position to make an "informed decision" about him yet. But also said "that's the whole point of this...grueling primary season," in the sense the lengthy process gives candidates time to show voters who they are and what they stand for.

"Mayor Pete is a perfect example of somebody who if you asked two months ago...well, you probably wouldn't have asked two months ago," Steyer added of Buttigieg, who's rapidly transitioned from being a longshot candidate to serious contender.

Buttigieg, 37, is openly gay, a veteran of the Afghanistan war, a Rhodes scholar, and multilingual. Recent polling from Morning Consult places Buttigieg in fifth place overall in a field of well over a dozen candidates, and tied with or ahead of heavy hitters like Sens. Elizabeth Warren and Cory Booker.

Buttigieg has also ranked third in recent polls in Iowa and New Hampshire — two early primary states — and raked in strong fundraising numbers early on relative to other candidates.

Read more: Billionaire Tom Steyer announces he's not running for president in 2020 and will focus on Trump impeachment campaign

Steyer, who's also known for his environmental activism, said that beyond Buttigieg he's also "very interested" in and has a lot of respect for the candidacy of Washington state Governor Jay Inslee, who's running a campaign focused on combatting climate change.

The billionaire and former hedge fund manager, who's leading a campaign to impeach Trump and was among the Democratic figures who received suspicious packages in October 2018, said voters are facing a completely different landscape than in 2016 when there were "realistically" only two people running for president on the Democratic side — former Secretary of State Hillary Clinton and Sen. Bernie Sanders of Vermont.

Relatedly, Steyer pointed to Sanders as "either the frontrunner or almost the frontrunner" at the moment and gives the senator a lot of "credit" for the campaign he ran several years ago as well as his current campaign.

"He is basically trying to stick to his guns in terms of the values that he represents and the policies that he supports. I think that he is doing a good job," Steyer said of Sanders.