I seriously doubt that this will affect the Dems negatively. Blacks as a whole reliably vote Dem no matter how negatively it may affect them.
Democrat Senator Strom Thurmond Filibusters the Civil Rights Act of 1957 with 107 Dems voting against it and only 19 Repubs voting no. = Blacks still vote Dem.
A full 80% of voting Republicans supported the Civil Rights Act of 1964 while 61% of Dems voted for it. Dems comprised 74% of the "no" vote. = Blacks still vote Dem.
Robert Byrd, a West Virginian Klansman became a Democrat US Senator and elected President Pro Tempore by his peers then celebrated upon death. = Blacks still vote Dem.
Democrat cities like St. Louis, Baltimore, and New Orleans are perpetually in the top spots for highest murder rate. Detroit has 30.6% of its citizens below poverty level. = Blacks still vote Dem.
All of this was witnessed within my parent's lifetime. There's a notion that Dems magically changed into a party that is "for Blacks" while Repubs became "against Blacks". This has been a useful bit of trickery for the Democrats which has been repeated through the years. If you can be surrounded by murder, poverty, lack of opportunity and vote for more of the same I can't imagine what would change the voting habits.