Europe’s center-right parties have embraced many ideas of the left: generous welfare benefits, nationalized health care, sharp restrictions on carbon emissions, the ceding of some sovereignty to the European Union. But they have won votes by promising to deliver more efficiently than the left, while working to lower taxes, improve financial regulation, and grapple with aging populations.

Europe’s conservatives, says Michel Winock, a historian at the Paris Institut d’Études Politiques, “have adapted themselves to modernity.” When Nicolas Sarkozy of France and Germany’s Angela Merkel condemn the excesses of the “Anglo-Saxon model” of capitalism while praising the protective power of the state, they are using Socialist ideas that have become mainstream, he said.

It is not that the left is irrelevant  it often represents the only viable opposition to established governments, and so benefits, as in the United States, from the normal cycle of electoral politics.

In Portugal, the governing Socialists won re-election on Sunday, but lost an absolute parliamentary majority. In Spain, the Socialists still get credit for opposing both Franco and the Iraq war. In Germany, the broad left, including the Greens, has a structural majority in Parliament, but the Social Democrats, in postelection crisis, must contemplate allying with the hard left, Die Linke, which has roots in the old East German Communist Party.

Part of the problem is the “wall in the head” between East and West Germans. While the Christian Democrats moved smoothly eastward, the Social Democrats of the West never joined with the Communists. “The two Germanys, one Socialist, one Communist  two souls  never really merged,” said Giovanni Sartori, a professor emeritus at Columbia University. “It explains why the S.P.D., which was always the major Socialist party in Europe, cannot really coalesce.”