MICHAEL WALSH: With Parties Polarized, Desire for Revenge Calls the Tune.

The people have spoken,” said former New York City mayor Ed Koch after the Democratic mayoral primary of 1989, “and they must be punished.”

The understandably bitter Koch had just been defeated by David Dinkins and was bidding his farewell to politics. And in fact, the people were punished: the one-term Dinkins, who defeated Rudy Giuliani in the general election that year to become the city’s first black mayor, saw crime soar on his impeccably tailored watch, with murders hitting a high of 2,605 the following year.

Four years later, even the Upper West Side had had enough and called the cops, in the form of Giuliani and his police chief, Bill Bratton.

Still, there was a hidden grain of truth in Koch’s famous crack: there is a vindictive element to Democrat electoral politics, especially in the 30 years since Hizzoner left Gracie Mansion. As the parties have polarized, a destructive element has entered our politics, and with malice aforethought. This will not end well.

Call it “punitive liberalism,” for lack of a better term.