Instead, Booker says he'll complete his second term as mayor (which runs until July 1, 2014), and that he'll "explore the possibility of running for the United States Senate." The difficulty there is that the Senate seat in question is already occupied by Democrat Frank Lautenberg, and Booker doesn't sound especially interested in primarying him—or at least, he doesn't want to come off sounding that way, for now, saying he "looks forward to consulting" with Lautenberg about his plans and adding that it would be a "privilege and honor to continue his legacy of service."
But Lautenberg is very old (88), and many New Jersey Democrats seem eager for him to retire. Booker's "exploratory" move may pressure Lautenberg to hang it up: If the flattery doesn't work, then the prospect of a bruising campaign against a much younger, energetic, and well-connected politician might convince Lautenberg he's better off handing things over to Booker than going out with a loss. And should Lautenberg look unexpectedly strong, Booker can always back down and bide his time, seeing as he's only 43.
Right now, though, Garden State Dems are going to be focused on defeating Christie, and at the very least, Booker's decision will give other candidates who've been considering a gubernatorial bid more certainty and allow them in turn to make up their minds. So far, only one person has declared (state Sen. Barbara Buono), but Booker's move may open the floodgates for other contenders. And while Christie looks formidable now, things can change a lot between now and next November.