Some version of this occurs almost everywhere Caroline Kennedy goes.

A perfectly well-intentioned person she has never met approaches her to say that a relative is entering politics because of her father, John F. Kennedy. Or expresses sympathy for the loss of her brother, John F. Kennedy Jr., who died in a plane crash in 1999, or her mother, Jacqueline Kennedy Onassis, who succumbed to lymphoma in 1994.

These interactions happen on the subway (the main way she gets around New York). They happen on Martha’s Vineyard (where she spends her summers). They happen at the ballet, at the movies, when she is on a book tour and when she’s visiting one of New York’s public schools, a cause she has been involved in for years.

Ms. Kennedy is said to be patient and gracious during these encounters, as she deflects and gently parries, leaving the other person feeling as if he or she has had a significant conversation, even if almost nothing at all was really said.

Sounds like perfect training for an ambassador.

On Wednesday, the Obama administration nominated Ms. Kennedy, 55, as the next United States ambassador to Japan, which would give her the kind of formal public role many have long predicted for her (but that had seemed permanently derailed by the off-and-on-and-then-finally-off flirtation with Hillary Rodham Clinton’s vacated Senate seat in 2009).