Thirty-six percent of Republicans now view Cain negatively, up from just 17 percent last month. He has also lost ground with Independents, 14 percent of whom are more likely to view him unfavorably, and Democrats, 22 percent of whom reported negative associations.

Americans also feel more passionately about their skepticism towards Cain. Twenty-three percent of those surveyed have "strong" unfavorable views of Cain, versus 11 percent who have "strongly favorable" opinions.

Still, there were a few encouraging signs for the former Godfather's Pizza CEO — the percentage of Americans who viewed him favorably was statistically equal to that of a month ago, falling to 29 percent from 31 percent. And half of Republicans see him more positively than negatively, by a 50 percent to 36 percent margin.

Cain has also shored up support among those who identify themselves as "very conservative," with his unfavorability rating rising only 7 percent with that group — far less than with other demographic groups. His support within that group can likely explain some of his resilience in the national polls: as Independents and undecideds have broken away from Cain, strong conservatives who are more likely to agree that the harassment claims were politically motivated have rallied around the candidate.

Nor, does it appear, do voters have that cheery an opinion of Newt Gingrich, the man many political analysts suspect will replace Cain as Mitt Romney's top challenger for the GOP nomination. Of those surveyed, 43 percent viewed the former House Speaker as somewhat or strongly unfavorable, versus 32 percent who held a favorable opinion — only marginally better numbers than Cain.

Still, it is unclear whether Cain will be able to weather the allegations, as slipping national poll numbers, coupled with his fall in favorability ratings, seems to betray a Republican electorate shopping for a new candidate. A CNN/Opinion Research poll released yesterday found Cain with just 14 percent of Republican support, trailing both Romney, leading with 24 percent, and Gingrich, in a close second place with 22 percent.