Sen. Claire McCaskillClaire McCaskillA Cabinet position for Petraeus; disciplinary actions for Broadwell after affair Defense bill tackles retaliation against military sex assault victims Red-state Dems face tough votes on Trump picks MORE (D), the incumbent in the race, defeated Talent in 2006; Talent had won a special election in 2002.

Akin seems increasingly unlikely to exit the race, however, releasing a new ad Tuesday morning asking for voters' forgiveness.

"I used the wrong words in the wrong way, and for that, I apologize," Akin said. “As the father of two daughters, I want tough justice for predators. I have a compassionate heart for the victims of sexual assault. I pray for them.”

Under Missouri law, the congressman has until 5 p.m. Tuesday to exit the race.