The dark money spending by political party makes the case that The Duopoly is pretty much a Republican/RW Libertarian monopoly.
However, the case for the corrupting influence of dark money on The Duopoly can be made by the coronation of Hillary in the 2016 primary. Her policies embraced some of the same positions espoused by The Republican Establishment. Only the unconventional cross-cut sawing of the Trump/Bannon insurgency interrupted the pre-ordained Uniparty ( Establishment ) outcome. There would be little coloring outside the lines allowed, except for Trump & Co.'s desire to shake down every gov’t institution, which the dark money has no problem with, as long as their fingerprints/DNA aren’t found at the crime scene.
Now that Trump has been exposed as a true criminal, in the coarsest sense of that word, he retreats to the crumbling shelter of the dark forces of the darkest money in American politics.
Trump hangs on by the thinnest of twine, supplied by these 1%er dregs . Dark money’s goal; it wants to drag democracy into a dark alley and strangle it, of course. Trump’s goal: no trial.
Trump’s got no problem with that 1%er goal, either. A guy turns a buck where he can these days. Then pays for protection. From the U.S. C. of C., no less.