An anonymous comment at Crooked Timber is trying to find a light at the end of the worst-case scenario tunnel, but I think we're going to have to have a definitional discussion, first. The question, paraphrased, is: assume that Bush is re-elected, and is really as bad as we think; are there historical examples"where an equally nasty group of people got into power but has since been gotten safely out of it?"
Nixon was their first approximation answer, but he was brought down by a rather specific set of circumstances rather than a broad movement. Someone suggested Ceauçescu, the object of the Romanian 'Velvet Revolution', but that raises the definitional question. Another commenter dismissed the suggestion on the grounds that Bush, even in an unrestrained second-term, three-branch-control state, couldn't be as bad as a communist dictator. In all fairness, they're probably right, though the increasingly loud cynicalvoice in my head also thinks that we shouldn't underestimate Bush and his circle, either.
That's the problem, isn't it? How 'nasty' is neo-imperialist evangelical Republican rule likely to be? Is it on a par with the de Gaulle years in France, or is it more like early Mussolini? How about FDR? Peron? Sandinistas? Franco? Disputed election, war footing.... This is one historical experiment I'd rather not run, to be honest.
Second Thoughts: One of the more interesting cases of political evolution within an unmodified constitutional system and without intervention from outside is Japan. The Meiji constitution, enacted in 1889, was designed to maintain oligarchic rule and provide the least possible democratic access to power while presenting the appearance of participatory process. But the 'power of the purse' turned out to be more substantial than they realized (there's a clause providing for the continuation of the previous year's budget if no budget is agreed upon, which would have prevented some of our showdowns and shutdowns, but which was unusable in that age of constantly rising budgets) and political parties gained access to cabinet posts, then oligarchs joined political parties, then political parties determined the PM, and things looked pretty democratic. There was about a decade of reasonably democratic rule over fifteen years, interspersed with 'emergency unity' governments, then things went downhill after the military embarked on its Manchurian projects. Not the most heartwarming story, in the long run, but that has more to do with the vagaries of an Imperial system; though we might call him a"Prince President", it isn't true, yet.