The fifth Democratic presidential debate on Wednesday put at least one pivotal 2020 factor into stark relief: the power of black voters in deciding the party’s nominee, and just how far many candidates in the still-crowded field have to go to earn their support.

Chief among those with work to do is U.S. Sen. Amy Klobuchar, D-Minn., whose past as a prosecutor has hindered more than helped her cause among black voters, who often see the criminal justice system stacked against them.

Last week, voters caught a glimpse of at least one Klobuchar strategy to make inroads in the black community: a focus on voting rights. At the Atlanta debate, Klobuchar repeated her call for people to automatically register to vote when they turn 18.

“If we had a system like this and we did something about gerrymandering, and we stopped the voting purges, and did something significant about making sure we don’t have money in politics from the outside, Stacey Abrams would be governor of this state right now,” Klobuchar said, making a pointed reference to the first black female major-party gubernatorial nominee in U.S. history.

Klobuchar joined four other candidates at a breakfast event hosted Thursday by the Rev. Al Sharpton’s National Action Network. She sought to link economic justice for minorities to voting rights — blaming gerrymandering for persistent inequities. And she underscored that economic justice won’t be possible if African-Americans can’t vote.

She brought much of the same message this fall to Milwaukee, where low black voter turnout helped tip Wisconsin to Trump in 2016. According to a Washington Post report, audience questions focused on her time as a prosecutor. Voters there also pressed her on how she would help poor residents rather than the middle class that they perceived to be her focus. She similarly struggled to win over the audience at an NAACP forum last summer in Detroit, where she was quizzed about whether she thought federal charges should have been brought against a New York police officer who killed Eric Garner in 2014.

To be sure, Klobuchar is not alone struggling to win support among black voters — especially in early primary states like South Carolina, where blacks are a major force in Democratic politics and where she hardly registers in the polls. Despite high levels of support among black voters, Joe Biden still faces questions over his support for the 1994 federal crime bill. Pete Buttigieg has been dogged by tense police-community relations during his tenure as mayor. Elizabeth Warren had to wait out demonstrations by dozens of black protesters from a school-choice group before delivering a post-debate speech in Atlanta, where she called for a “full-blown national conversation about reparations” for slavery. And Bernie Sanders is trying to avoid being shut out by black voters who crippled his fast start in the 2016 primaries.

The message being sent from the Deep South to Milwaukee and Detroit: Black voters will have a lot of say in who challenges Donald Trump in 2020.