WASHINGTON (AP) — Republican presidential candidate Herman Cain has drawn a line in the sand, and now he's hoping it sets like concrete.The Georgia businessman has responded to allegations of sexual harassment with a series of definitive statements that invite closer scrutiny of his past conduct. Cain insists "there's nothing else to dig up" about his past.It may well be that Cain has nothing to hide. But a number of politicians have been derailed after issuing public invitations to check out their conduct.Most famously, Democratic presidential hopeful Gary Hart got in trouble after he challenged reporters to follow him around in 1987 after questions arose about whether he'd been stepping out on his wife.Cain's denials raise the stakes for the businessman-candidate if anything else comes out.