Actor Mark Ruffalo, a supporter of Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE, praised the Vermont senator late Sunday after Sanders clashed with Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE in the latest Democratic presidential debate.

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"He was charming, he was direct, he felt fresh in his answers," Ruffalo said in a post-debate appearance on MSNBC. "I just felt a lot of heart from him."

"He awoke something in me, and it was his ideas, and it's his decency, and it's his record, frankly," Ruffalo added.

"This guy is exactly who he's always been, he's always been fighting for the little guy, and today that just happens to be the very person we need," Ruffalo said.

"There's an authenticity about him and about his history and about his career as a politician that speaks to me."

Sanders and Clinton tangled on the auto industry and water during the debate Sunday night held in Flint, Mich., which has been under the national spotlight for months over its water contamination crisis.

Both Democratic candidates called for the state's Republican governor, Rick Snyder, to step down and be held responsible for the situation. They also weighed in on accountability for Environmental Protection Authority officials.

Ruffalo, an anti-fracking activist, was also active on Twitter on behalf of Sanders, saying that Sanders was "crushing it" at the debate while stating that "Clinton supports fracking" while Sanders "does not."

The actor also weighed in on the possibility of Sanders facing off against Republican presidential front-runner Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE in the general election.

"There's no doubt in my mind he could beat Donald Trump if he goes up against him," Ruffalo told MSNBC, adding that he thought the self-described democratic socialist would "mop the floor" with Trump.