With Senator John Kerry leaving the Senate, this opens up the chairmanship of the Senate Foreign Relations Committee. The next in line is Senator Barbara Boxer, of California, who would then have to give up her chairmanship at the Environment and Public Works Committee. If she does make the switch, then the next in line at EPW is Sen. Carper of Delaware, who would then have to relinquish his chairmanship at the Homeland Security and Governmental Affairs Committee. The next in line there is Sen. Pryor of Arkansas, and being a committee chair could certainly help him in his reelection contest in 2014.
Of course, if Sen. Boxer stays put, an unlikely scenario given the prestige of being chair of Foreign Relations, Sen. Menendez of New Jersey is next in line there.