Rep. Bill Cassidy, R-La. (right), poses with his family and House Speaker John Boehner at the start of the new Congress, on Jan. 3. On Wednesday, Cassidy announced that he would challenge Democratic Sen. Mary Landrieu in 2014.
Credit Paul J. Richards / AFP/Getty Images
Sen. Mary Landrieu, D-La., on Capitol Hill in December.
Sen. Mary Landrieu of Louisiana, considered among the most vulnerable of the Senate's red-state Democrats facing 2014 re-election, now has at least one potential Republican opponent, Rep. Bill Cassidy, whose congressional district includes Baton Rouge.