The collapse of the 20th Century Synthesis and the rise of the 21st Century Social Crisis have less to do with partisanship than they have to do with the unchallenged hegemony of a single class. Call that class what you will, the ruling class, the 1%, the new robber barons, the bourgeoisie, it's all the same. Whether through their own action by power of their ownership status, through their constantly increasing leverage and domination of the political system, or by taking advantage of unfolding social and economic processes, since the writing of the Powell Memorandum, the class of Capital has been on a total class war footing, almost utterly unopposed. Through their scorched earth policies, and the cravenness of the political elite that has enabled them every step of the way, the interests, ideologies and institutions of every other sector of society have been either obliterated, coopted, or rendered helplessly marginal to serve as convenient scapegoats PRN. Today there is not a single institution of meaningful influence in our society that does not commit 100% of its energies to the promulgation and perpetuation of the interest and ideology of the ruling elite.
Our political system as we know it emerged from the doctrines of those like Madison, who believed our society would always be characterized by a multiplicity of factions, each with its own realm of interests, constantly in ebbing and flowing interaction and conflicts among themselves. So the system was designed to channel those factions into loose, fluid aggregations that through alliances of convenience would tend to modulate the power any single group in society could wield. The only entity they believed could hold hegemonic power would be the state acting in and of itself, and therefore they imposed strict limitations on the extent of state power.
What the simple, homogeneous, largely agrarian society of the Federalist period could never have foreseen was the massive development of social and economic forces on the continent in the past 200 years. Those forces, those means of production and communication, have increasingly concentrated in a smaller number of hands (by deliberate action), giving their holders power far exceeding that any single faction that Madison could have imagined, power great enough to exercise total control of the state power itself. By a single faction gaining that level of influence and control, Madison's system fails. Solution sought within the framework of Madison's system must likewise fail, must be doomed from the outset. You cannot use a broken tool to fix itself.
As long as this overwhelming power and control remains in the hands of a single faction, any nominal change in control of government office will only represent a personnel change among those whose function is to serve the power of that hegemonic faction. Until that hegemonic power is broken, politics in the Madisonian model will not only fail to represent any other than the capitalist class, it will serve as an active vector of frustration and despair for those who seek solutions to the problems of any other class within the thoroughly compromised system.