DUBLIN — Oscar Wilde still lounges, louche-like, on a boulder in Merrion Square. As always, the Liffey, a river crossed by bridges named for playwrights and patriots, lumbers its way to the sea. Grafton Street is packed with moneyed pedestrians. But Irish ayes are missing.

The Gathering, as they call this year, is a campaign backed by the government and the tourism industry to induce the clamorous clans of Erin to pay a visit here. Given that half the world is Irish and the other half wants to be, in Bill Clinton’s phrase, it’s an easy sell.

Yet, what should be a year of discovery, a diaspora of 70 million summoned to the home of their not-so-distant ancestors, is clouded by a bittersweet anniversary. Fifty years ago the last king of Ireland, President John Fitzgerald Kennedy, came to the land of his great-grandfather Patrick. A few months later, he was gone, shot by an assassin in Dallas.

To look back now, at a time when Ireland and the United States are staggered by doubt, is to realize how much has changed in the half-century since he was here -- change, in too many respects, for the worse.