In the final insult of a devastating 2014 election for Democrats, Sen. Mary Landrieu, the party’s last remaining statewide officeholder from the Deep South, was trounced Saturday in the head-to-head Louisiana Senate runoff election. Republican Bill Cassidy’s resounding victory is the ninth Senate seat picked up by the GOP in this year’s elections, three more than the party needed to take control of the chamber. With nearly all the ballots counted, Cassidy led Landrieu by 14 points, 57 percent to 43 percent.