Fresh off the primary campaign trail, McCaskill fired off ads against Akin characterizing him as too extreme for Missouri.
Akin, of course, made his own campaign stumble when he told a reporter a woman's body has a way of shutting down a pregnancy in instances of rape.
While Republican outside groups appear to have spent more on elections than Democrats this year, records show they got less bang for their buck in races across the country.
In a new analysis, the Sunlight Foundation estimates that only 1 percent of the money Karl Rove's American Crossroads dished out went to winning candidates. And the U.S. Chamber of Commerce and the American Future Fund, two more GOP-leaning groups, also poured millions into races that didn't pan out for them.
"Karl Rove's reputation is going to take a significant hit. If Crossroads was a business and Rove is the CEO, he would be fired for getting a poor return for his investors," says Democratic Sen. Chuck Schumer. "My greatest surprise in the election was that the PACs had less of an impact then I feared."
But Bill Allison, editorial director for the Sunlight Foundation, says that big money still had an impact even if the GOP didn't win big.
"It may have made a lot more candidates competitive that wouldn't have been. It caused a flood of fund-raising by members of Congress," Allison says. "It may not have had the effect donors wanted it to have, but it still had an impact on the political process."
Some GOP strategists argue that huge Super PACs lost their momentum because they invested most of their efforts on advertising in already saturated markets.
In 2016, Allison says Super PACs will have to regroup and focus on a new strategy.
"Obama's campaign had a great get out the vote operation. They had personnel across the country and tools for identifying voters. I wouldn't be surprised if the next time around you see Super PACs building that kind of system," Allison says.
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Lauren Fox is a political reporter for U.S. News and World Report. You can follow her on Twitter or reach her at firstname.lastname@example.org.