The California Guv and his Florida counterpart went at each other onstage during the Fox News debate hosted by Sean Hannity -- but the 1.5-hour conversation took an unusual turn when DeSantis brought up poop on the sidewalks of San Francisco.

DeSantis held up a photo of the excrement-laden Northern California city, explaining that human waste on the streets is a way of life now in SF.

The 2024 Republican presidential candidate also pointed out that Newsom only cleaned up the City recently for a visit from Chinese dictator Xi Jinping.

Newsom appeared flustered, nervously laughing and calling it all nonsense.

The "Great Red State Versus Blue State Debate" had some other tense moments, like when DeSantis accused his Democrat rival of running a shadow campaign for prez.

But, Newsom didn't take the bait, throwing his support behind current president and 2024 democratic frontrunner Joe Biden. He pointed to Biden's record of creating "fourteen million jobs, 10 times more than the last three Republican presidents combined.”

DeSantis then took aim at Biden's US-Mexico border crisis, saying the Democrats are lying to the public about the issue as millions of undocumented migrants have poured into the country.

Newsom returned fire, blasting DeSantis for busing migrants from the Texas border to Martha's Vineyard “so that you can out-Trump Trump.” He then mocked DeSantis' poll numbers, saying, "You’re down 41 points in your own state."

There were more fireworks when DeSantis botched the name of VP Kamala Harris. Newsom quickly corrected DeSantis and chastised him ... “Shame on you. It’s Madame Vice President to you.”

The governors also attacked each other on crime, taxes, abortion, environmental protections and the Coronavirus pandemic.