Going into this election, Claire McCaskill was considered one of the most likely Senators to lose re-election due to a move towards Republicans by Missouri voters in previous elections.
Todd Akin won the Republican primary in an upset. Akin was helped either by the intense media war between Sarah Steelman and John Brunner, or by an ad run by McCaskill during the Republican primary calling Akin "too conservative".
In the days after the primary, Akin had a lead on McCaskill in the polls. Until he had an interview with Charles Jaco on St. Louis TV. Questioned on his stance regarding abortions in the case of rape, Akin referred to "legitimate rapes" and said that the body would "shut itself down" and prevent pregnancy.
These comments led Republican leadership and SuperPACs to call on Akin to withdraw from the campaign. These groups also pull supported from Akin for much of the fall campaign.
Akin withstood these calls for the period of a month between the primary and the setting of the final ballot. During this time, McCaskill laid low, trying to not force Akin out of the race.
After the ballot was set, McCaskill and her allies displayed their monetary advantage by running ads reminding voters of Akin's comments and how they tied into his deeper record on issues.
Most public polling showed the election to be a slight McCaskill lead. But on election day, McCaskill won by over 15%, amassing the most votes of any candidate running in Missouri in that election.