Perhaps one day we will forget the parlaimentary seating arrangements which occurred after the French Revolution, but until then, we have at least some psychological means of measuring the distance between Left and Right (no matter how absurd the distinction is at the end of the day). If either position exists in exclusion of the other, it is only to the degree that it has expended with the other. While what constitutes each may accrue a different definition over time, one thing has always seemed certain to me: each position contains the other within it. They are divided so far as they, at once, refuse to coexist and seek to enforce their ways onto the other. One may say the Right values culture while the Left says that capital is choking culture, therefore let's worry about that latter (or another way around it, that culture is simply a plastic construction). One may say the Left values social harmony while the Right claims that the Left seeks to eliminate all of its enemies in order to see its harmony come to fruition. Both are guilty of realizing the world through a totality they have imposed on it; of not seeing that kernel of their enemy within. Both push war to the realm of speculation and all the while continue to wage it in the actual present. Both sides go through their oscillating eras of accepted radicality. Both are susceptible to crowdism and mob-think. Both become old world values and give ample opportunity for the younger generation to swing the opposite direction.
Granted, now and again, both positions will appropriate features which, architecturally or ontologically, do not fit very neatly into the Left-Right scheme, but which are well fitted to radical, philosophical interpretations of their respective position, such as some in the radical Right favoring monarchy and certain brands of anarchy having been adopted by the radical Left.
Whether one deals with a monarch who promises to act on behalf of the people or a representative parliament, we are still in the arena of mindless singularity. The individual himself is a composite of different drives and inclinations all warring for supremacy in man's breast. It may well turn out that, at least on a topical level, the representative body of government is little different than the corporeal body of man. Just as one man may be the equivalent of a river rather than a being, so are governments with their endlessly changing laws.
If spirituality is the struggle to align the mindless drives to the higher calling of a configuration that is as noble as it is complete and self-purposive (whether one calls this configuration Yahweh, Attman, Tao or Logos), then politics are a means of pushing those borders even further, though without the benefit of that self-contained configuration offered by spirituality. Politics is left with the job, not of organizing self contained-units, but becoming the one conglomerate of un-self-contained, mindless drives. In this sense is politics anti-spiritual: it opens the door to the body but traps it in a room in which it can only smell the musk of provision.