Scott Brown got into the U.S. Senate two years ago declaring, “This is not the Kennedys’ seat,” but 2012 could be the Year of the Kennedys’ Revenge. Joseph P. Kennedy III’s likely congressional run in the redrawn 4th District, which includes Brown’s Wrentham hometown, has Democrats buzzing about a new generation of Kennedys helping Elizabeth Warren take back the late family patriarch’s Senate seat. With Warren already running even with the Republican incumbent in the polls, even a small wave of Kennedy nostalgia, especially on Brown’s strongest turf, could sweep the Democratic challenger to victory in November. The prospect also...