But his record of their doings isn’t mere namedropping. More importantly, Schlesinger manages to convey the excitement and optimism that they once exuded. In recent years, debunking the Kennedys has become more fashionable than praising them; Teddy Kennedy, now gravely ill, has long felt like a throwback to the distant past. But in 1961, Kennedy’s White House rocked with parties. At one, Schlesinger records, there were ‘about 80 guests, Lester Lanin’s band, and we stayed until nearly three in the morning,’ something hard to imagine in staid, teetotaling, post-9/11 Washington. The next morning, Schlesinger and a colleague go to meet some visiting Europeans, and all agree that ‘the discussion is recommencing,’ in Washington, that things are getting interesting again; the following few days Schlesinger spends working on a plot to overthrow Castro. Lunchtime martinis, champagne at dinner, a sense of endless possibility, a feeling of enormous confidence and everybody is under 50. Sounds like fun, no?

Take away the martinis, swap Lester Lanin’s band for the Black Eyed Peas, and it also sounds a lot like the Washington many hope Barack and Michelle Obama will now recreate. There is the same whiff of racial progress in the air, the same appeal to young people, the same optimism — despite the worst economic crisis in a generation — and the same sense that ‘things will change’. Schlesinger’s diaries show how potent that combination of feelings once was, and thus provides an explanation by analogy for the mood of the present.

He also shows what the aftermath could look like. The latter part of the book, post-Kennedy assassinations, is significantly gloomier. Schlesinger describes the paranoid madness of LBJ, the unpleasantness of Watergate, the disappointment of Jimmy Carter — whom he loathes — and his almost unbearable nostalgia for the glamour of the Kennedys. One wonders whether Obama’s advisors be writing memoirs like this 50 years from now.

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