09/02/2014 11:31 am ET

Residency Issue Could Rock Key Races

Tom Williams via Getty Images

Louisiana Sen. Mary Landrieu is one of the most vulnerable Democratic incumbents this cycle, and her re-election race is one of the most watched. It is not only expected to be a long one, as a December runoff seems likely, it could also play an instrumental role in determining which party controls the U.S. Senate next year.

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