Stepping aside from whether Cain is going to be the GOP candidate or not, and stepping aside from the guilt or innocence of Cain with respect to the harassment allegations being brought against him, let's look at the claim Cain makes about what's behind his accusers. Cain claims it's the Democrats. True or not, there is a pathway to that claim making sense.
Ask any Democrat and they'll tell you the one candidate they fear going up against is Mitt Romney. That's ridiculous on the face of it - Romney isn't even solid in his support with the Republican base. Mitt Romney has flip-flopped on a number of issues and he's behind Romneycare - the precursor to Obamacare. As far as Mitt Romney goes, Democrats are loaded for bear. They'll be ready for him. They want to face him.
Ask Democrats who they think the GOP nominee will be and they tend to say Mitt Romney. If I'm a Democrat political operative, and I'm gearing up to face one candidate, it's in my best interest to help that candidate become the nominee.
Herman Cain meanwhile, started to occupy the perceived vacuum of conservatism in the GOP field as the viable not-Romney. That becomes a threat to the president's re-election strategy which is to build up a war chest and run against a candidate they are prepared for and believe is very beatable. Go back a few weeks and everyone was talking about his 9-9-9 plan. Cain's numbers were very strong and seemingly on the rise. Not now.
It is possible that those Democratic operatives saw the Cain threat to Romney as being a real threat to the Obama election strategy. Digging up some dirt on Cain and getting it out to the press is a logical tactical response to Cain's rise. Five accusers have come forward now. All it takes to get that ball rolling, is one. Truthful or not, there's smoke there and the hope is that it will precipitate a fire. The fire is more accusers (motivated by greed or by possible actual grievances, it doesn't matter) coming forward and the real fire, is the public perception turning on Herman Cain. If that was the plan, the mission may be accomplished. If it isn't it certainly has time to ferment during the primaries and if Cain eventually does become the nominee, there's fodder for the general campaign - not from Obama but by proxy.
Could Democratic operatives be behind this move? Definitely. It doesn't mean they were though. Despite a strong denial offered by Cain, the real damage might turn out to be making that claim about Democrats, without being able to turn that smoke into some real fire.