Not so long ago, Republicans hoped that Mr. Christie’s electoral victories would provide a durable boost to the party. After nearly a decade out of power, Republicans were offered a toehold in Trenton and help competing in difficult areas of the state, including populous northern New Jersey.

Yet over the last year, some of the governor’s signature political trophies have been stripped away. A landmark pension-reform deal was struck down in court, denting Mr. Christie’s image as a problem solver.

Mr. Christie, who was first elected thanks in part to his profile as a clean-cut prosecutor, is now stuck parsing legalisms in an effort to play down his administration’s culpability in the events that led to the federal indictments last week…

Despite periods of intense personal popularity, Mr. Christie has had only limited success at lifting the prospects of other Republicans. In 2013, the party made a major push to win control of the State Senate, hoping to ride Mr. Christie’s political coattails as he romped to re-election. Though he won a second term by more than 20 percentage points, Republicans failed to pick up a single seat in the chamber.

Still, the sheer breadth of Mr. Christie’s victories appeared to hold out the possibility of a larger political shift. In 2009, he won his first election by a wider margin than any Republican since Thomas H. Kean’s landslide re-election a quarter-century earlier.