He may as well. Whether Cain is guilty as sin or innocent as a lamb, or any degree in between, his candidacy has been destroyed by this smear campaign. Continuing will run up large debts, and all losing politicians find those difficult either to pay or to escape.
The more interesting question remains. Who is behind these unsubstantiated accusations of sexual misconduct? They haven't all cropped up spontaneously, nor are the leftie media e.g. Politico doing it indendently. My money's on that sleazy Obama operator Axelrod, but we can't rule out an equally unethical retardican pro working either for Romney or the party establishment.