Ted Widmer is assistant to the president for special projects at Brown University. He recently edited “Listening In: The Secret White House Recordings of John F. Kennedy.”The last of John F. Kennedy’s extraordinary troika of speeches in June 1963 occurred on this day, 50 years ago.With each, he broke new ground. On June 10, at American University in Washington, he sketched a vision of coexistence with the Soviet Union, strikingly at odds with the more bellicose messages of 1961 and 1962. On June 11, in a televised address, he endorsed the civil rights movement and promised a bill, far in advance of what any president had done, and in advance of where he himself was a few months earlier.On June 26 he came to Berlin, on one of the most frenzied days in the history of the Cold War. A huge crowd — estimated at 1.1 million, or 58 percent of Berlin’s population — came out to see him.