PARIS — Paris. - The left, all but extinguished in the United States during the 1980s, when bearers of the dreaded ''liberal'' appellation were pitilessly hunted down in their congressional districts, has survived the same decade very nicely in Western Europe. Now troubles have begun there, but of a different order than in the U.S.
Socialist parties have governed Spain and France for all, or nearly all, of the past decade. Social Democrats continue to dominate Scandinavia, and provide a plausible and electable opposition in West Germany. Italy's Socialists have emerged as challengers to the Christian Democrats, as that country drifts toward a constitutional crisis.
The French and Spanish Socialists both were outsider forces in the 1970s, Spain's Socialist Party having been illegal and clandestine in the 1960s. Two decades later, as the 1990s began, both had come to seem the ''natural'' governing parties of their countries. Conservative forces had been routed.
But what might be called the Decennial Curse has struck both (a phenomenon identified by Mrs. Thatcher in the early 1970s, when she said that 10 years was about as long as a democratic public will put up with a given leader -- as she was herself subsequently to validate). The European Socialists are in difficulties less for what they have done as for what they have become in 10 years.
Power has wasted both, as was to have been expected. Scandal has accumulated in how the parties are financed, and scandals of favoritism, nepotism and of personal corruption.
The French case has produced ''that endemic French affliction called malaise . . . a volatile mixture of ennui, anxiety and irritation with the potential for triggering sudden acts of collective furor'' (as Time magazine's Frederick Painton describes it). A professor and leading French foreign-relations expert says, ''One expects the Right to be corrupt. But when the Left is corrupt too. . . . '' He leaves his sentence apocalyptically incomplete, its implications unspeakable.
A famous business figure, Pierre Berge, head of the Yves Saint Laurent empire, and of the Paris Opera as well, has just accused the Socialist Party of capitulation to the values of demagogy and speculation. ''What is the Left if not a morality, a standard? It is that for which we voted. That is why people hoped and struggled to build its success.''
The party's crisis results from more than money scandal. It expresses a powerful moral conflict on the issue of immigration. The new prime minister, Edith Cresson, has chosen to discuss this matter in language which had a devastating effect, first of all upon her own party, although she actually said only that existing law (a Socialist law) concerning illegal immigration, political asylum and repatriation, should and would be enforced.
There are those Socialists, of whom she is one, who believe that what President Mitterrand himself once called a ''threshold of tolerance'' for culturally and racially distinct immigration has been broached in France, and that for the sake of social peace immigration must be sharply restricted and persons illegally in .. France sent home. This, of course, is what nearly all of the Right thinks and says, and it certainly is what the National Front of Jean-Marie LePen says.
On the other hand many Socialists believe it the moral obligation of a rich nation like France to accept high levels of immigration and make generous provisions for immigrants. They are bitterly against Mrs. Cresson. However the vigor of the argument itself has demonstrated that the Socialist Party is not only alive but in aggressive form, fighting over real issues of power and society. In this respect it looks in considerably better condition than the Democratic Party in the United States, still in the coma provoked by the Reagan Revolution.
The French (and Spanish) Socialists appear to have the stuff of survival: The capacity to adapt program to reality, and to lose an election but come back in the one after that. The Democratic Party does not show the same vital signs. President Bush might be struck down by political lightning (evidence of an Iranian arms-prisoner deal struck during the 1980 presidential campaign, proof that Mr. Bush knew about illegal contra financing, etc.) but that would give the Democrats victory only by default.
They would not deserve victory, as they have failed to make an intellectual recovery from their Vietnam ordeal, the '60s social revolution and its bad-tempered and socially divisive aftermaths, the Iran humiliation, or the Republicans' successful and continuing exploitation against them of the United States' haunted inheritance of race and slavery: the issues of quotas, ''multi-culturalism,'' self-segregation and resegregation, drugs, urban crime.
The French Socialists had to survive their own colonial war (Algeria was the Socialists' Vietnam), a doomed opposition to the Gaullist revolution, Marxist intoxications, a sentimental Third-Worldism, a near-total lack of modern economic grasp as late as 1981-82. Power is a great educator and they learned fast.
But as the Decennial Curse shadows them, they can reasonably hope that if they are defeated, the defeat will be temporary, and that their divisions will inspire a healing reconquest of power. A decennium of opposition has failed to produce such a result for the Democratic Party in the United States. The intellectual and moral energy doesn't seem to be there. The Democrats might have something to learn from the Left abroad, since the issues that currently work in the United States seem all to belong to the Republicans.
But who in America -- except for the English professors -- looks abroad for an idea?
William Pfaff is a syndicated columnist.