I don’t think that Christie is afraid to lose reelection if the Senate election was on the November ballot—the sacrificial-lamb Democrat running against him has no chance. What Christie wanted to avoid was the Senate race becoming the big-ticket item in November, drumming up Democrat (particularly black) turnout and helping the Democrats hold both houses of the state legislature. With the gubernatorial race the only really big contest, and Christie winning big, he might be able to sweep in GOP majorities in the Senate (which would allow him finally to appoint two new members of the state Supreme Court) and House. And, yes, Christie could have declared that the special election wouldn’t be held until November 2014, but if he did that the NJ Supreme Court likely would have ruled that it had to be held no later than November 2013 and scheduled it for the same date as the gubernatorial and legislative election, so he preemptively had to pick a date prior to this November.