Akin's introduction to the state's voters has been overwhelmingly negative, considering that less than a month ago, he was viewed favorably by 24 percent of likely voters -- and unfavorably by only 11 percent.
McCaskill's 9-point advantage on the ballot test is fueled by gains among most subgroups, but particularly among women. In the July poll, the two ran neck-and-neck among female voters: 47 percent for McCaskill, 46 percent for Akin. Now, the Democratic incumbent leads by 18 points among women, 55 percent to 37 percent.
Akin still manages to retain the support of nearly four-in-five Republicans, but independents have soured on his candidacy, turning against him in a nearly-30-point swing. He led McCaskill by 11 points among independents a month ago, but now he trails by 17 points.
Asked whether Akin should withdraw from the race "in the wake of his comments about rape and abortion," 47 percent believe he should, while 37 percent say he should not. This is particularly interesting when broken down by respondents' vote preferences. McCaskill voters actually prefer that he remain in the race by an ever-so-slight margin, 44 percent to 40 percent. But half of Akin supporters think he should drop out, while just 34 percent think he should stay.
Most damaging to any hopes that Akin could eventually compete is the fact that, among voters undecided on the ballot test, two-thirds want him to withdraw.
McCaskill's lead is a testament to the damage caused by Akin's remarks. She remains less-than-popular, as slightly more voters view her unfavorably (41 percent) than favorably (39 percent). And, despite worries that Akin's remarks could also harm the candidacy of presumptive Republican presidential nominee Mitt Romney, the former Massachusetts governor leads President Obama, 50 percent to 43 percent. Obama's favorable-unfavorable split of 38 percent-48 percent is worse than McCaskill's.
The poll -- the first public, live-caller survey since Akin's Sunday comments -- was conducted Wednesday and Thursday, surveying 625 likely voters. The margin of error is plus-or-minus 3.9 percentage points.