President Obama nominated Caroline Kennedy, daughter of former president John F. Kennedy, to be ambassador to Japan.

Kennedy, whose early and strong support for Obama’s 2008 bid gave his candidacy a key boost in helping him win the nomination over then-front-runner Sen. Hillary Rodham Clinton, had been expected to get a top job in the administration.

Wednesday’s official announcement, anticipated for several months, comes after Tokyo recently gave its approval to receive the first woman as U.S. ambassador to Japan.

Washington, to show how much it values the bilateral relationship, has usually sent highly regarded elder statesmen to the country.

Kennedy’s predecessors include luminaries, such as former Senate majority leader Mike Mansfield, former vice president Walter Mondale, former House speaker Tom Foley and former Senate majority leader Howard Baker.

And while the former first daughter does not have their legislative experience — and scant experience with Japan — Camelot is well-remembered in that country.

John F. Kennedy’s moves to improve relations with Japan — including dispatching Robert F. Kennedy on a mission to repair ties and naming scholar Edwin O. Reischauer as ambassador — are fondly recalled.

But, if confirmed by the Senate, Kennedy would be taking over at a time when the ­U.S.-Japanese relationship is once again frayed over the U.S. military presence there and other security and economic issues.

Kennedy is a lawyer and president of the John F. Kennedy Library Foundation. She also chairs an advisory committee at the Institute of Politics at Harvard University.

She was a longtime member of the board of directors of the NAACP’s Legal Defense and Educational Fund.