Dinkins?
Sinkin' Dinkins.
He was so bad, he paved the way for the fascist Giuliani, whose biggest accomplishments were cracking the heads of squeegee guys at the Lincoln Tunnel and showing up for photo ops after the 9/11 debacle he helped create.
Dinkins wasn't ineffective because he was black. He was ineffective because he couldn't unite the disparate neighborhoods that make the city what it is.
The current mayor is Sinkin' Dinkins v2.0.