 In late 2010, Bruning announced that he would run in the 2012 election for the U.S. Senate seat held by Democrat Ben Nelson, whose approval ratings in Nebraska had plummeted after he provided the 60th and final vote necessary to break a Republican filibuster and pass the Patient Protection and Affordable Care Act.In December 2011, Nelson announced that he would not seek reelection.Bruning was seen as the strong front-runner in the Republican primary race; former Attorney General and current State Treasurer Don Stenberg, favored by the conservative Tea Party movement, was seen as his strongest challenger.