The fight between Biden and Sanders for the Democrat Party’s presidential nomination is intensifying as the two candidates campaign in the midwest this weekend ahead of primary votes in states like Michigan and Missouri in the coming days.

Speaking to donors in Bethesda, Maryland, Biden seemed to call for a positive battle between him and Sanders, but he also managed to get in some digs on the Vermont senator and his supporters.

“I know I’m going to get a lot of suggestions on how to respond to what I suspect will be an increasingly negative campaign that the Bernie brothers will run,” the former vice president said. “But we can’t tear this party apart and re-elect Trump.”

What we can’t let happen is let this primary become a negative bloodbath

Following his victory in South Carolina, Biden has become the frontrunner for mainstream Democrats, with former rivals Pete Buttigieg and Amy Klobuchar dropping out of the race and endorsing him. Biden seemed to suggest at a campaign rally in Missouri that an endorsement from Senator Kamala Harris is also happening, though she has made no official announcement.