A debonair 40-something Senator, with a toothy smile and a lofty turn of phrase.A made-for-television First Family. A fashion-forward First Lady. Generational change at a time of national self-doubt. No wonder the chatter in Washington is of a Black Camelot, with Barack Obama cast as Jack Kennedy, and his wife, Michelle, playing Jackie.Stepping before the press for the first time as President-elect, with his heavily pregnant wife looking on, JFK joked that he looked forward to a new administration and a new baby.Barack Obama, of course, produced a similarly memorable flourish by promising his girls a new puppy.By strange coincidence, these two young presidents - JFK was 43 when he took the oath of office, while Mr Obama will be four years older - have also inherited a comparable set of challenges.In 1960, after eight years of Republican rule, the US economy had flat-lined (though admittedly it was not in its present, doom-laden state), American diplomacy was in urgent need of renewal, and the nation's self-certainty had been rocked by the launch in 1957 of Sputnik 1, a showy piece of galactic one-upmanship which fuelled fears that the Kremlin was winning the Cold War.