Sen. Claire McCaskill (D-MO) finds herself down against all three potential Republican opponents in her re-election bid, a new poll released Saturday shows.  

A new survey from Mason-Dixon, conducted on behalf of the St. Louis Post-Dispatch and News 4, shows would-be Republican challengers John Brunner, Sarah Steelman and Todd Akin all topping the first-term senator.  McCaskill trails Missouri businessman Brunner, 52-41 percent,  former state treasurer Steelman, 49-41 percent, and US. House Rep. Akin, 49-44 percent.  

The Missouri Republican primary will be held on August 7.  Mason-Dixon's poll shows Brunner leading among likely Republican primary voters with the support of 33 percent.  Steelman picks up the support of 27 percent, while Akin polls at 17 percent.