Democratic Sen. Claire McCaskill walks off the stage with challengers Republican W. Todd Akin (left) and Libertarian Jonathan Dine after their debate in the Missouri Senate race in Columbia, Mo., on Sept. 21. (Associated Press)

Democratic Sen. Claire McCaskill walks off the stage with challengers Republican W. Todd Akin (left) and Libertarian Jonathan Dine after their debate in the Missouri Senate race in Columbia, Mo., on Sept. 21. (Associated Press)