The latest population estimates from the U.S. Census Bureau shows New Jersey as likely to lose one congressional seat for the 2012 election.  New Jersey's estimated population is 8,707,739 - up 3.5%, but not enough to keep the state's thirteenth seat.  That would increase the size of each district from 647,258 in 2002 to 725,645 in 2012.  Unless someone retires, New Jersey will either see an incumbent vs. incumbent general election, or an incumbent vs. incumbent primary. 

In 1992, when New Jersey went from 14 seats to 13, two incumbents were put in the same district.  A primary was avoided when Bernard Dwyer (D-Edison) retired instead of facing Frank Pallone (D-Long Branch) in the Democratic primary.  New Jersey went from 15 seats to 14 in 1982, but the district represented by Millicent Fenwick (R-Bernardsville) was eliminated when she entered the race for U.S. Senator.