If you are an American over sixty, you remember when you learned that John F. Kennedy had died. If you are one of my contemporaries—too young to have experienced Kennedy, too old to be a cynic about his aura—you may recall a different snapshot, of the moment you thought Jack Kennedy had been reborn in the form of some youthful contender who could turn an inspirational phrase and stab a finger in the air.

Your moment might seem absurd now: Gary Hart in the glow of winning New Hampshire in 1984. Or bittersweet—the November night in 1992 when Bill Clinton retired the WWII generation. Yours might be agonizingly recent – Barack Obama on a dream-lit stage in Grant Park in 2008. It’s been the longest quest in modern politics, the effort to recreate an ideal of power that was extinguished exactly 50 years ago, and it has never ended well.

Pretenders like Hart imitated the style without Kennedy’s strength of purpose. Clinton, Kennedy’s equal as a tactician, never matched his capacity to lift the country’s moral tone. As for Obama, he has gone steadily backward in terms of his hold on the public’s imagination. Kennedy did the opposite, expanding a one vote per precinct squeaker into the last presidency that never dropped below fifty percent approval.

The consistent take on Kennedy, which Chris Matthews argues in his 2011 book “Elusive Hero” and Thurston Clarke reprises in his recent effort, “JFK’s Last Hundred Days”, is that the late president’s genius was his disdain for conventional wisdom, whether it was about the grip of the decaying boss structure in his party, the permanence of the Cold War, or the rigidity of social barriers like racism. True, as is their assessment that JFK never stopped growing and adjusting to circumstances: he reversed his worst blunder, the Bay of Pigs, with his mastery during the Cuban Missile Crisis, and one doesn’t have to share Clarke’s cherry picked rendition of Kennedy’s last few months to appreciate that the leader who died in Dallas was wiser and more substantial than the image-meister who barely left a footprint in the Senate.

But Kennedy’s strategic deftness in avoiding war with a country that no longer exists surely is not what resonates with this post-nuclear generation: nor is the hedging on civil rights and Vietnam that kept his popularity intact the quality that frames him as an exemplar of presidential vision. To account for why he still outranks all of his presidential peers in public esteem, to find why a presidency whose early days exist only in black and white newsreel still resonates, requires understanding two other elements of Camelot.

First, Kennedy is the last president who consistently challenged rather than promised. JFK’s successors have outdone themselves in bidding to give us more of what we want – the liberal ones offering more entitlement, the conservatives offering to return more tax dollars to us, or to restrain your tax dollars from being squandered on “them”. Kennedy read the country’s mood as less self-absorbed than that, and America rewarded him.

And then there is the fact that Kennedy managed to invigorate his supporters without ever really pitting Americans against each other. The rhetoric of politics has been set on a different course ever since: modern liberals describe a country weighted down by privileged interests that have stacked the deck; modern conservatives paint a picture of a society under siege from permissive forces who are burdening success and undermining our values. You can search Kennedy’s speeches in fine detail, and the trait that is missing is a demonization of his domestic antagonists.

He must have been tempted: dogs were being marshaled against children in Birmingham, southern governors were re-litigating the Civil War, and can anyone dispute that the Republicans of his day genuinely were Neanderthals on poverty and health care? That Kennedy resisted the urge to define American politics as a clash of light versus darkness yielded a practical dividend for him – no president since has enjoyed consistently high approval ratings from his rival party – but it was also borne out of the skepticism the old war hero had for blood-feud ideology.

The ironic side of Kennedy no doubt admired Shakespeare’s passage about the Welshman who brags that he can “call spirits from the vasty deep,” and the rejoinder that “So can I, so can any man. But will they come when you do call them?” More than a few charismatic politicians have issued their share of high-flown calls. The last one we have answered, and kept answering, is John Kennedy.

A version of this essay was published in Politico in November, 2011.