House Minority Leader Nancy Pelosi (D-CA) Getty Images

Billionaire Tom Steyer, one of the leading Democratic donors in the 2018 election cycle, has plenty of praise for House Minority Leader Nancy Pelosi, D-Calif., but he stopped short of publicly supporting her to lead the party in Congress after this year's midterm elections. Steyer, the founder of the nonprofit NextGen America, a group that supports progressive policies on climate change and health care, told CNBC in an exclusive interview that Pelosi has been the "perfect" leader for the party. However, he would not say outright that she should remain in charge, regardless of what happens this fall. "Nancy is my congressperson. I have enormous regard for her professionally and personally. I think she is astonishingly good in terms of running the Congress and as a Democratic leader," Steyer, who is also from California, said after being asked whether Pelosi should remain the House Democrats' leader.

Pelosi, a former House speaker, is a favorite target of Republicans, particularly as the GOP fights against a possible blue wave this fall. Some Democratic candidates — including Conor Lamb, who just won a special election to flip a deep-red Pennsylvania seat — have declined to support Pelosi to be the party's leader in the House. When asked again whether he would back her based on the outcome of the congressional midterms, Steyer didn't budge. "I think that is a whole bunch of hypotheticals that I have no idea the outcome of," Steyer said. "Nancy is doing an incredibly good job in terms of rallying people in November. She's stood up in a lot of issues and gotten pilloried sometimes for that." A spokesman for Pelosi declined to comment for this story. Steyer has donated to Pelosi in past races, including when she ran for re-election in California's 12th District in 2016. During that cycle, he gave $48,800 to her joint fundraising committee, the Nancy Pelosi Victory Fund. Steyer gave $32,500 to the same group in 2011, according to Federal Election Commission filings. In June 2017, Steyer and his wife hosted the Democratic Congressional Campaign Committee's Speaker's Cabinet Dinner and Discussion in San Francisco with Pelosi. The event raised a total of $593,500 for the DCCC.

Tom Steyer holds one of his Need to Impeach town hall meetings on March 20, 2018, in Largo, Md. Jahi Chikwendiu | The Washington Post | Getty Images

To impeach or not to impeach?

Yet Pelosi and Steyer haven't seen eye to eye recently on one particular issue looming over the Democratic Party: The prospect of impeaching President Donald Trump. Steyer has become the leader in an effort to push for Trump's impeachment. He backs an ad campaign and initiative called "Need to Impeach." Pelosi has been skeptical of the effort. At a recent press conference on Capitol Hill, the Democratic leader specifically addressed the calls from Steyer's supporters to move ahead with campaigning on a goal of impeaching Trump, arguing that it's premature while special counsel Robert Mueller's probe is ongoing. "I don't know that they're talking about impeachment, but whether they have the facts and the law to make a determination of how they go forward — we don't have that information," Pelosi said then.

Still, Steyer's impeachment efforts are ongoing, and he's not afraid to support candidates outside the Democratic establishment in order to push his $40 million campaign against the president. Sen. Dianne Feinstein, D-Calif., one of the longest-serving senators, is one of Steyer's most recent targets. He recently backed her primary opponent, California state Senate President Pro Tempore Kevin de Leon. Steyer's endorsement came less than two months before the June 5 primary and could give de Leon the financial boost he needed to upset Feinstein. Steyer told CNBC that he has no regrets about the decision and that he supports de Leon because of his work on climate-change initiatives. He also said the Democratic establishment has shortchanged de Leon. "He had been a huge climate leader, huge labor champion, a real nationwide leader in terms of immigrants' rights and we just felt like, in addition to everything else, we felt he wasn't getting a fair shot by the establishment," Steyer said. Steyer and his wife, Kathryn, have contributed more than $16 million so far in 2018 to campaigns through a variety of committees and nonprofits, according to the Center for Responsive Politics. That's second behind Republican megadonor Richard Uihlein and his wife, Elizabeth, who have given $25 million. — Graphic by CNBC's John Schoen

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