Black mayors are getting white votes and white mayors are getting black votes.

In 1983, Wilson Goode became the first African American to be elected mayor of Philadelphia, my adopted home town. Defeating incumbent Frank Rizzo, a former police commissioner and a notorious race-baiter, Goode won a whopping 97 percent of the black vote. 

Fast forward to last month, when former city councilman Jim Kenney won the Democratic primary — and, for all practical purposes, the mayoralty — in Philadelphia. Kenney is white, but he split the black vote about evenly with the African American runner-up, state Sen. Anthony Williams. 

And that’s good news for all of us. Ever since the 1960s, when African Americans entered mayoral politics, most urban residents have cast their ballots along rigidly racial lines. But things are changing, and not just in the City of Brotherly Love. 

In the 2013 Democratic primary in New York, Bill de Blasio — who went on to become mayor — got the same percentage of the African American vote as black candidate William Thompson. And in Chicago’s run-off in April, white incumbent Rahm Emanuel defeated Hispanic challenger Jesús García by winning over a third of the votes in Latino-majority communities. 

That reverses the historic pattern, in which each race simply rallied behind its own. And it’s almost impossible to govern an American city on that basis. ...