Sen. Mary LandrieuMary Loretta LandrieuCassidy wins reelection in Louisiana Bottom line A decade of making a difference: Senate Caucus on Foster Youth MORE (D-La.) is headed to a runoff against Rep. Bill Cassidy (R-La.), complicating Democrats’ chances of holding onto the seat.


With 24 percent of precincts reporting, Landrieu had just 41 percent of the vote, while Cassidy took 42 percent, according The Associated Press. Tea Party-backed Rob Maness had 13 percent of the vote.

The runoff could ensure that the battle for control of the Senate remains an open question until Dec. 6.

Under Louisiana’s jungle primary rules, all candidates, regardless of party, face off on the same ballot in November, and if no candidate takes more than 50 percent of the vote, the top two vote-getters head to a runoff.

Democrats have long admitted that their best shot at a win in Louisiana was on Election Day and that retaining the seat would become tougher in a runoff.

While battle-tested Landrieu was initially seen by Democrats as one of the party's strongest incumbents, the increasingly conservative state worked against her. Republicans poured millions of dollars into attack ads tying her to President Obama, despite her efforts to show her independence, as well as support from some local Republicans.

And her main argument in the race, that her clout as chairwoman of the Energy Committee was invaluable for the state, was unable to overcome distaste for Obama in Louisiana.

Cassidy, meanwhile, ran a largely noncontroversial campaign, arguing his medical background made him the best contender to take on ObamaCare.