Sen. Claire McCaskill (D-Mo.) trails all three of her potential Republican rivals, according to a new survey conducted for two Missouri news outlets, cementing her status as this cycle's most vulnerable incumbent.
Businessman John Brunner (R) holds the largest advantage over McCaskill, leading by a 52 perent to 41 percent margin. Former state Treasurer Sarah Steelman (R) leads by a 49 percent to 41 percent margin. And Rep. Todd Akin (R) leads by a 49 percent to 44 percent margin.