The new ad titled ‘Broken Trust,’ opens with a clip of McCaskill at a town hall meeting in 2009, as she seeks to defend President Obama’s Affordable Care Act.
The video shows McCaskill asking voters if they trust her, only to be shouted down by many in the crowd.
The video then airs an audio clip of Obama saying he is proud to have McCaskill as a supporter. It concludes with a clip of McCaskill saying “You've got every right, if I decided to run again, to do everything in your power to fire me."
A source familiar with the ad told CNN it would air in every market in Missouri.
The McCaskill campaign dismissed the ad, accusing Akin of trying “once again to mislead voters” about McCaskill’s record because “he knows his own beliefs are just too extreme for Missouri.”
"Missouri families know exactly who they can trust to protect Medicare, Social Security and student loans, and it's not Todd Akin,” said Erik Dorey, a spokesman for the McCaskill campaign, in a statement. “Claire's always been a Senator on our side, fighting to protect these safety nets. On the other hand, Todd Akin's been working to abolish the minimum wage and eliminate Social Security and Medicare, all while protecting tax giveaways for mega-millionaires and big oil at the expense of working families.”
Akin quickly apologized for the comments, but rejected calls from many top Republicans, including GOP presidential candidate Mitt Romney, to stand down from the race.
Republicans fear Akin could cost them a chance at recapturing the Senate this November. But buoyed by support from social conservatives, Akin has said he will continue his campaign.
A new poll this week suggests the Missouri Republican is still competitive. A Rasmussen poll finds him trailing McCaskill by 6 points, with 43 percent support to her 49 among likely voters.
This story was updated at 1:00 p.m.