Don't forget the material basis for these shifts! While The Discourse of "practical" truangulating centrists tends to show this rightward path, it is because (1) they were already fundamentally reactionary, they tend to just use this logic as an excuse for why they tolerate far-right positions, and (2) the right is supported by the ruling class to address some of the "problems" it creates, like a marginalized underclass that wants enough income to feed their children, housing, and safety from violence.
The shift right is not driven simply by debate or ideology, but by the arenas where degradation in material conditions due to capitalism meet the ruling class' need to deflect blame to the marginalized (who they can reap larger profits from) to placate the less marginalized. Racism, nationalism, and extermination campaigns are created and maintained for the interests of capital, with the common people being pushed and prodded to fall in line with repeating the (usually ad hoc) new or recycled scapegoats and underclassrs. Wouldn't want you to point blame in the right direction!