For what it's worth,
the polling from Missouri shows Akin leading by 11 points (51-40) in the last poll released before the "legitimate rape" comments on August 19. That poll, from SUSA, is uncommonly good for Akin, but a) he had still led in every poll listed here since March, and b) SUSA's last poll of this race ended up almost exactly right on the final margin. McCaskill takes a lead within a week of the comments, and Akin's best poll after that is a 5 point lead, with McCaskill ahead in every poll after mid-October.
With all of that being said, I'm inclined to say it's entirely possible Akin could have won, or at least kept it within a few points, if he hadn't said it. (Granted, I was only a kid when it happened, but I recall absolutely overwhelming backlash to that interview and it being basically all anyone knew him for.)
Poll
