McCaskill, who is seeking a second term, asserted Akin has an "extreme record" on women's issues, education, Medicare and Social Security, among other things. It's "moderate versus extreme. I think there's a very big choice for Missourians to make," she said.
Akin, a congressman from suburban St. Louis, stressed that McCaskill was one of Obama's earliest supporters in his 2008 campaign and backed his health care and stimulus proposals, which he said have driven up the deficit. "She was his strong right hand," Akin said.
The hourlong debate before an audience in the Clayton High School auditorium in suburban St. Louis contained nary a mention of the reason why Missouri's Senate race was propelled into the national spotlight. In mid-August, Akin drew widespread condemnation for remarking in a TV interview that women's bodies have ways of avoiding pregnancy in cases of "legitimate rape." He apologized and forged ahead with his campaign despite calls from top Republicans - including presidential candidate Mitt Romney - to drop out.
Asked after Thursday's debate why she didn't bring up Akin's rape remark, McCaskill told reporters that everyone already had heard about it and to mention it "would look maybe like piling on." Akin left immediately after the debate without talking to reporters.
The candidates remained largely cordial throughout the debate but closed with some personal accusations that were factually shaky.
Akin claimed McCaskill "transferred $39 million to her home business." That was a reference to an Associated Press article that found that businesses affiliated with McCaskill's husband, Joseph Shepard, received $39 million in federal housing subsidies during her first five years in office. McCaskill voted for some of the bills - and against others - that funded the departments that provide the subsidies. But the AP found no evidence that McCaskill directly steered any money to her husband's firms, and McCaskill's campaign has said none of that money made it into the family's personal bank accounts.
McCaskill closed the debate by asserting that female staff in Akin's congressional office made 23 percent less than male staff members. McCaskill's campaign released an analysis showing that Akin paid his male staffers an average of $15,872.12 per quarter and his female staffers an average of $12,872.12 per quarter over his 12 years in office. But during the most recent quarter, Akin's female staffers appeared to earn more on average than his male staffers, according to an online listing of salaries.
McCaskill also asserted that "Akin voted to raise his pay." But pay raises in Congress occur automatically, and many of the votes McCaskill referenced were procedural ones that ended debate on bills, thus preventing consideration of potential amendments attempting to reject automatic raises.
During their answers to questions from panelists and audience members, Akin and McCaskill repeatedly differed on the proper role of the federal government.
McCaskill, for example, criticized Akin's prior statements in support of abolishing the Education Department and his opposition to a 2010 law that gave the federal government - not banks - direct responsibility for issuing student loans.
"The federal government's involvement in education is important for our country," McCaskill said.
Akin countered: "Claire McCaskill seems to think this is a crisis if you don't have everything done by the federal government."
Akin said the federal school lunch program could be administered by states, quipping that the food probably wouldn't taste any different to students.
Asked later if there were any misconceptions the candidates wanted to clear up, McCaskill said it was wrong for Akin to imply she is not willing to stand up to Obama. She said she opposed some of his energy policies and had wanted him to quickly approve the Keystone XL pipeline to bring oil from Canada to the U.S.
"I don't even agree with my mother 98 percent of the time, much less the president of the United States," she said.
On a topic that hadn't previously received much attention in their race, McCaskill said she supports all forms of stem cell research. Akin said he opposes human embryonic stem cell research, because he believes life begins at conception.
Quarterly financial reports released earlier Thursday show Akin raised $1.6 million from mid-July through the end of September and had about $553,000 remaining in his account at the start of October. That significantly trailed McCaskill, who raised $5.5 million during the period and still had about $2.1 million left in her campaign account.