Thanksgiving week is a milestone for Barack Obama, but not one that many are likely to commemorate. The president who seemed poised to inherit John F. Kennedy’s mantle—in the eyes of Kennedy’s last surviving child and brother as well as many optimistic onlookers (me included) in 2008—will now have served longer than his historical antecedent. Obama, surely, does not want to be judged against any JFK yardstick, longevity included. It’s his rotten luck that he incited such comparisons at the start by being a young and undistinguished legislator before seeking the presidency; by giving great speeches; by breaking a once-insurmountable barrier for African-Americans, as Kennedy did for Roman Catholics; and by arriving in the White House with his own glamorous wife and two adorable young children in tow. He has usually shrugged off these parallels gracefully. These days, with his honeymoon long over, it’s particularly in his interest to do so. But Obama can’t escape JFK’s long shadow, and neither can we. Another wave of Kennedyiana has arrived just in time for the holidays: three major new books, all three already best sellers. But in the second decade of the 21st century, what, exactly, are the customers buying?

Camelot would seem one of the last go-to articles of national faith for Americans at a time whenthree quarters of them believe the country is on the wrong track. The Kennedy enterprise still perennially engages the imaginations of high-end artists as various as Don DeLillo, James Ellroyand Stephen Sondheim—not to mention an irrepressible parade of television-mini-series hucksters who come up with such ideas as casting Katie Holmes as Jacqueline Kennedy. The assassination alone has generated more books than there were days in the Kennedy presidency. And the Kennedy cult, as Gore Vidal called it in 1967 when he waded through an early bumper crop of New Frontier memoirs, generally gets a waiver on reality checks.

But if the JFK story has resonance in our era, that is not because it triggers the vaguely noble sentiments of affection, loss, and nostalgia that keepers of the Kennedy flame would like to believe. Even the romantic Broadway musical that bequeathed Camelot its brand is not much revived anymore. What defines the Kennedy legacy today is less the fallen president’s short, often admirable life than the particular strain of virulent hatred that helped bring him down. After JFK was killed, that hate went into only temporary hiding. It has been a growth industry ever since and has been flourishing in the Obama years. There are plenty of comparisons to be made between the two men, but the most telling is the vitriol that engulfed both their presidencies....