This can also be predicted in terms of realpolitik. If the power of nations tends to consolidate along predictable lines, then the political question at any mom

This can also be predicted in terms of realpolitik. If the power of nations tends to consolidate along predictable lines, then the political question at any moment is reduced to a left-right "rate of reform" along each axis, with the furthest right positions being near-zero rates of change, but all viable positions serving the purpose of ensuring power for the stakeholders. This makes the right tend to automatically converge onto a mythologized moment in the past where their power is greatest - rights of kings, supremacy myths, and so on, while the left goes in a spectrum of directions but must ultimately form a singular coalition in order to gain power. Thus the prevailing tendency of left-right politics is also one of leaps forward from the left and gradual slides back from the right as the coalition breaks down. The new consensus is different from the old, but it's also typically not the most ideologically left one, since it emerges to compromise with the present realities, and the more radical you go, the more it resembles blood-in-the-streets revolution, which is a huge roll of the dice. The developed world as a whole seems to be approaching one of those "great leap" moments today as more and more issues have fallen into partisan extremism, motivating the search for a new consensus.