New York Magazine has more:

Whenever a Senate seat becomes available in Massachusetts, at least one Kennedy — any Kennedy, doesn’t really matter who — must, by law, at least consider running for it. With John Kerry’s seat opening up soon, Ted Kennedy Jr. has fulfilled this sacred duty, but today the Globe reports that he won’t run, partially because he lives in Connecticut, which is not the same state as Massachusetts. Ted Kennedy’s widow, Victoria Kennedy, has also been rumored as a possible candidate. When asked by the Hill on Friday about her intentions, she had no comment.