Simon Hix has published graphs showing the percentage share accruing to different ideological families in European elections since 1918.
The first thing that strikes one is how constant things have been, all things considered. There was a Radical Right spike in the early 1930s, and a longer-term Radical Left resurgence following the war that petered out half a century later, but otherwise preferences have been remarkably steady.
Some might be concerned about the modern day Radical Right surge, especially since it appears to be far more stable than the fleeting one during the Great Depression. However, its worth emphasizing that the Radical Right today are essentialy the Conservatives of yesteryear. For instance, here is what Charles de Gaulle had to say about multiculturalism:
It is very good that there are yellow French, black French, brown French. They show that France is open to all races and has a universal vocation. But [it is good] on condition that they remain a small minority. Otherwise, France would no longer be France. We are still primarily a European people of the white race, Greek and Latin culture, and the Christian religion. Those who advocate integration have the brain of a hummingbird. Arabs are Arabs, the French are French. Do you think the French body politic can absorb ten million Muslims, who tomorrow will be twenty million, after tomorrow forty? If we integrated, if all the Arabs and Berbers of Algeria were considered French, would you prevent them to settle in France, where the standard of living is so much higher? My village would no longer be called Colombey-The-Two-Churches but Colombey-The-Two-Mosques.
Compare and contrast with his ideological successor, Nicolas “Le métissage obligatoire” Sarkozy.
The Left, too, has grown far less hardcore. Nationalization of the commanding heights of the economy and some degree of openness to central planning characterized Social Democracy a half-century ago and earlier. Now they’re just a slightly different shade of the neoliberal center, while most Communists now abandoned the class struggle in favor of various SJW inanities.