The allegations of sexual harassment that have dogged Herman Cain for a week have taken their toll on his presidential campaign, according to a poll by Reuters/Ipsos.
In the first sign that the claims, which date back to a decade ago when he was head of the National Restaurant Association, have begun to damage his election chances, the poll shows a drop in his popularity among Republicans from 66% a week ago to 57%.
Among all registered voters, Cain's favourability declined 5 percentage points, from 37 to 32.
A majority of respondents, 53%, believe the allegations, despite his denials. Among Republicans, 39% believed them to be true.
"The most striking thing is that Herman Cain is actually seeing a fairly substantial decline in favourability ratings towards him, particularly among Republicans" said Chris Jackson from Ipsos.
The Republican presidential candidate, who had been enjoying a surge in the polls which made him the latest challenger to frontrunner Mitt Romney, is struggling to draw a line under allegations that he sexually harassed at least three female employees when head of the association. Two women reportedly received financial settlements after the incidents.
Cain has given conflicting accounts of the claims since they were first published by news website Politico last week. He denies the allegations.
However, an attorney for one of the women has since rejected his denials and said Cain had subjected her to "inappropriate behaviours and unwanted advances."
Cain, speaking to reporters on Saturday night after a debate in Texas, said he would not provide any more answers.
But fellow Republicans urged him to get everything out in the open soon.
GOP presidential candidate Jon Huntsman, appearing on NBC's Meet the Press, said he needed to "get the information out and get it out in total."
"Legitimate questions have been raised and that information has to come forward", he said.
Haley Barbour, Republican governor of Mississippi, also weighed in, suggesting that Cain needed to clear the air before moving on.
"What he wants to do is get back on message," Barbour said, "and the way to do that is to get all the facts on the table and get it behind him."
Fellow presidential candidate Ron Paul said that the media's coverage of the allegations were distracting voters from more important issues.
"The media blew this way out of proportion" he said on Fox News Sunday.