Liberal filmmaker Michael Moore expressed his concern that former Vice President Joe Biden won't excite Democratic voters enough to defeat President Trump in November.

Moore, who was an outspoken supporter for Sen. Bernie Sanders, I-Vt., appeared on MSNBC before the official kickoff of the Democratic National Convention and was asked to react to comments he made in 2019, warning Democrats that Biden was "this year's" Hillary Clinton and that he was "not going to excite the base," highlighting women, people of color and young people.

While the Oscar-winning documentarian conceded on Monday that Biden his polling best among voters ages 18-35, he still had reservations that the presumptive Democratic nominee can pull off a victory against Trump, who Moore famously predicted would win the 2016 election.

MICHAEL MOORE WARNS DEMS ABOUT A TRUMP REELECTION: 'HE KNOWS EXACTLY WHAT HE'S DOING'

"Even your own poll today, the NBC poll, showed that [when] asked 'Why are you voting for Joe Biden,' 58 percent said because he's not Trump. That's the number one reason," Moore told "The Beat" anchor Ari Melber. "So I look at that and I worry because people do need to get excited."

The "Fahrenheit 9/11" director then weighed in on Biden's selection of Sen. Kamala Harris, D-Calif., as his running mate.

"I was shocked that he picked Kamala Harris, frankly," Moore said. "I thought for certain that he would swing to the right and pick Susan Rice. Instead, he swung to the left and picked Kamala Harris."

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Moore's description of Harris' politics conflicts with descriptions made by some in the mainstream media, who have called the California senator a "pragmatic moderate" and a "small-c conservative."

Back in May, Moore warned Democrats that Trump could win reelection.

"We need to behave as if he will win a second term," Moore told "Real Time" host Bill Maher. "Anybody who right now says, 'Oh no,' you're really part of the problem because you're not taking this seriously. He knows exactly what he's doing. He was just in Michigan this week. It's the third time he's been in Michigan in three weeks. He believes he's going to somehow pull this off."