Cain is likely done IMO.
It’s not the credibility of the allegations, but the damage done by the allegations themselves.
If that is the case, then conservatives are done for. The left will use any means to win. Mud will be dredged up or invented against each serious candidate in turn and whoever is left will not be a serious threat to Obama or the leftward movement of the "Republicrat" party.
The only damage being done here is by those who are saying that Cain is toast because of false allegations brought against him. I will continue to support him based upon integrity. It is a shame that you choose instead to allow the liars to dissuade you from supporting truth.