For Obama, the controversy provides a much needed chance to motivate his base, particularly young, unmarried women, who polls show are more likely to stay at home this election.
"It's not that they disagreed with him but this could potentially be the impetus to get them out of the house," Lawless says. "The stakes are a little easier to identify – if the Democrats lose the Senate and Mitt Romney is president, it impacts Supreme Court justices, something people do care about. And this is a litmus test issue."
Though initial polling since Akin's comments show him still leading McCaskill in Missouri, it's likely the real damage – up-and-down the ticket – won't show up until advertising on the issue gets underway in earnest.
Rebekah Metzler is a political writer for U.S. News & World Report. You can contact her at firstname.lastname@example.org or follow her on Twitter.