Spain and Italy were semi-peripheries, social democracy flourished in fully industrialized countries, so the situations are not really comparable. If by "radical Leftist" you mean one-party states or authoritarian mass parties -- well, those social formations are mostly gone forever, with a few exceptions in the industrializing world (and even there, one party states are on the way out).
^^^^^ CB; Fact check: China is the world's leading " industrializing" country suggesting that a Communist Party state is the best model for social formations in the immediate future. Is Vietnam suffering under the current world crisis ? If not, there is another achievement of a Communist Party state. Russia seems to be objectively a one party state still, also. The multiparty status of former socialist countries seems a charade mocking multiparty forms in the older bourgeois nations of Europe and America.
Two and multiple party states, like the US or Greece, are not showing the Third world that their are model for future success.
The one party Communist state form would seem to be the way to go now, especially as the Communist control is favorable for future transition from capitalism to socialism.