AS A VOTER, I have two rules of thumb: (1) I don't vote for incumbents, and (2) I don't vote for Kennedys. Rarely do I violate either rule, but on Tuesday I had no choice: In the Democratic Senate primary in Massachusetts, the incumbent, Ed Markey, was being challenged by a Kennedy and I could oppose only one of them. So I voted for Markey — that is, against Joe Kennedy III. Which made mine one of the 765,000 votes that ended Kennedy's congressional career — and, let us hope, the Kennedy political dynasty. I have nothing against Kennedy personally....