IN the spring of 1969, President Nixon met in the Cabinet room with ten mayors of American cities. They were nothing if not a variegated lot, mixing party, religion, race, region in the fine confusion of American politics. They had been chosen to be representative in this respect, and were unrepresentative only in qualities of energy and intelligence that would have set them apart in any company. What was more notable about them, however, was that in the interval between the invitation from the White House and the meeting with the President, four had announced they would not run again. The mayor of Detroit who, at the last minute, could not attend, announced his noncandidacy in June.