Pennsylvania’s top two Democrats called Saturday on state Treasurer Rob McCord to pull the racially charged attack ad he is airing against rival Tom Wolf in the gubernatorial primary.

Rendell said the spot was “one of the worst I have ever seen,” adding that it was a style of politics “that makes me ashamed to have been part of this business for most of my adult life.”

The 30-second spot blast’s Wolf for serving as campaign chairman for the 2001 reelection campaign of York Mayor Charlie Robertson, who was indicted the day after the primary on murder charges in the death of a black woman during the city’s race riots 32 years before, when he was a police officer.

Sen. Bob Casey said the ad was “offensive” and slanders Wolf’s character by implying he is insensitive to racism. “Tom is a man of uncommon integrity, with an abiding sense of fairness and justice,” Casey said in an interview.

McCord brushed aside the criticism in a late-afternoon news conference, saying that the issue provided a “teachable moment” about the need to confront racism that is more important than a campaign’s tactics.

“If I were to lose support from more people than I gain from it, I would be proud to have started this discussion,” McCord said, accompanied by his wife, Leigh, at the headquarters of AFSCME Local 1199 in Center City.