Harris could easily be the most unpopular VP only because she pisses off both sides. To the right she's a black woman and that's plenty to hate her. To the left, she's a statist cop who put plenty of poor people in jail over tiny drug crimes. As the DA of San Francisco and AG of California she played a typical neoliberal role: executing conservative policies with flowery liberal verbiage.

Progressives don't like her and the DNC doesn't listen to their progressives often. She's definitely a sore spot.