Former California Governor Jerry Brown (D) warned Democrats running for president that their constant attacks on President Donald Trump are “not all that interesting” to voters.

“Trump is not popular here, that is an understatement, but after a while, when it’s only attacks on Trump, that doesn’t feel like there’s much substance there,” Brown told the New York Times. “It’s a very thin debate right now, as I see it, and for many Californians, and I’m sure many Americans, it’s not all that interesting.”

Brown is in the camp that wants Democrats to make broader appeals to working-class voters in states like Wisconsin, Michigan, and Pennsylvania to take back the White House.

But many left-wing activists believe the way to defeat Trump in 2020 is to activate and turn out the left-wing base by making everything about Trump.

They have been emboldened by Rachel Bitecofer, “a Christopher Newport University professor who accurately predicted that Democrats would flip 40 House seats in the 2018 midterm elections,” who believes that a Democrat will win the White House in 2020 because the Democrat will begin the race with 278 Electoral College votes.

Bitecofer, citing her election model, said she thinks this is the case because Democrats in Midwestern states that Trump barely carried in 2016 will no longer be complacent in 2020 due to “negative partisanship.” She argued this week on MSNBC that “the election of Donald Trump is a needed kerosene on” a “lazy and complacent Democrat electorate” and the time when candidates could “persuade large swathes of the electorate over has passed.”

“I’m not saying that moderates aren’t important or that there aren’t moderates, there certainly are and they can be appealed to – although Democrats don’t do it well – but really it’s all about the base,” Bitecofer concluded.