Sen. Cory Booker (D-NJ) this week previewed some potential lines of attack against former Vice President Joe Biden and Sen. Bernie Sanders (I-VT), taking issue with the former’s support for the 1994 Crime Bill and the latter’s lukewarm support of Hillary Clinton in 2016.

Booker, who has struggled to gain traction in the polls, wrapped up an RV tour of Iowa on Monday and the New Jersey senator reportedly reminded voters during his trip that a lot of Democrats like Biden have actually made things worse for people by supporting legislation like the Crime Bill, which Sanders also supported.

“I’m one of those Democrats to say we need to start doing things that make people’s lives better, because Democrats have done things that have made people’s lives worse,” Booker reportedly said, referring to the Crime Bill, according to the New York Times.

Booker then referenced the bad blood between Sanders and Clinton in 2016, asking Iowans to ask every candidate whether they will “double down” and back the party’s 2020 nominee as establishment Democrats are reportedly getting worried that Sanders will again be a spoiler if he does not secure the nomination.

“I hope that one of the questions you ask every single candidate is, if you’re not the person, that you will commit to us that you will double down and support the person who is the nominee,” Booker reportedly said. “I saw that movie in 2016. I don’t want to relive it.”

Biden’s main argument on the stump has been electability, and Booker reportedly argued that “getting rid of Donald Trump” should just be “the floor, not the ceiling.”

But Biden is the frontrunner and Booker’s campaign of “radical love” has failed to resonate because the party’s voters are preoccupied first and foremost with ousting the president they loathe.

During his campaign kickoff event, Biden warned progressives that the first plank of his climate platform is “beat Trump” because none of the policies they value will be enacted if Democrats do not defeat Trump.

It is a message that has also been resonating with the party’s critical African American voters who have backed Biden over Booker and Sen. Kamala Harris (D-CA) in every state and national poll.

The most recent Tel Opinion Research South Carolina poll, conducted May 22-24, found Biden is clear frontrunner with 37%. More importantly, Biden had an astonishing +84% favorability with African American voters in the poll and was the top choice of 44% of African American voters in the critical first-in-the-South primary state.

The poll also found that “when compared to Biden,” both Harris and Booker “lack the intensity behind their positives that Biden enjoys with African Americans.”