He can get away with it because The Republicans are the anti-African American party. They opposed Civil Rights, to this day they put in voter supresion laws to stop none white voters voting, their gerrymandering deliberately suppresses the effect of the black vote, they opposed integration and voted against black kids being bussed to white schools, Republican held states massively divert funding away from black schools to white schools, they are the party that marched against the country’s first bi-racial President and elected an overt racist. Trump also took out 5 adds asking for the execution Central Park 5. These were young black boys (14-16 IIRC) wrongly convicted of the gangrape of a white girl due to coerced interogation.
However Biden should be working harder giving voters a reason to come out and vote for him, rather than stay home.