Paris — The French Communists may have something to learn from their Italian comrades: that success in West European politics is in inverse proportion to closeness to Moscow.
The French Communists' decision last week to quit the government was only the latest act in a long, difficult script for this strongly pro-Moscow party.
After an all-night debate between the ''reformists,'' who reasoned that leaving the governing alliance would mean retreating into a political ghetto, and ''hard liners,'' who argued against remaining in a government preparing to impose another round of capitalist austerity, nobody seemed happy with the decision to pull out.
The party is in disarray. Electoral support is at its lowest level in half a century, and the rank and file are split over ties with Francois Mitterrand's Socialists as well as the party's autocratic leadership and its strong links with the Soviet Union. The party garnered only 11 percent of the vote in last month's European Parliament elections.
In Italy, in contrast, the Communists gained 33 percent of the vote in that election, coming in ahead of the Christian Democrats for the first time.
The ideologies of Western Europe's two largest Marxist formations are as different as their electoral results. When the Italian Communists began shaking loose from Moscow some three decades ago, the French Communists continued to describe the Soviet Union as a model.
And in the last decade, when the Italians began emphasizing free internal debate, the French kept insisting on ''democratic centralism'' - discussion within the Central Committee, but not outside.
''For a quarter of a century, the French Communist Party has progressively distanced itself from the political realities and social changes in France,'' says Jean Ranger, a specialist in communism at the Centre National de la Recherche Scientifique. ''Their decline is long term.''
In the last 10 years, the deterioration has accelerated. In 1974, the Communist Party was still the dominant force of the French left. It was overtaken by Mr. Mitterrand's Socialist Party only in 1976.
As late as 1979, the Communists still had the support of 20.6 percent of the French electorate. But in the presidential elections of May 1981 their vote slumped to 16.1 percent. Since then the decline has worsened.
Party leader Georges Marchais blamed the party's continued membership in the government coalition. He argued that the Communists, as junior partners in Mitterrand's Socialist-led coalition, were being held accountable for the government's unpopular economic austerity policies, policies that ran counter to party orthodoxy.
Beginning in 1983, Marchais criticized with increasing vehemence the government's decisions to cut public expenses and let unemployment rise. Mitterrand's bold plan to trim France's heavy industries, announced this spring, increased his anger. Most of these industries lay in traditional Communist Party strongholds.
For Marchais, then, the die seemed to have been cast long ago. He had come to believe the only way to stop the decline was for the party to quit the government and regain its full freedom to criticize Mitterrand's economic austerity.
But he recognized the dangers. The Communists would lose the legitimacy of holding four Cabinet posts. And the timing of the break would be crucial: Marchais did not want to cause the collapse of the union of the left.
Mitterrand's appointment of Laurent Fabius as prime minister last week with a mandate for more austerity provided Marchais with a convenient opportunity to leave.
Not all Communists agree with Marchais's analysis, however. The reformist faction argued that the party is paying for its failure to break with Moscow. To revive its fortunes, the reformers say, the French party should follow the Italian model, instituting greater internal democracy and emphasizing its independence.
In this logic, the best immediate course of action would have been to stay in the government while replacing party leader Marchais.
Last month, Marcel Rigout, then Cabinet minister for vocational training, told journalists the party needed ''a cultural revolution.'' He said the party was losing support from young people because it was identified with Soviet prison camps and he suggested Marchais had a large responsibility for the electoral decline.
In the end, most party bureaucrats backed Marchais. The party left the government, Marchais stayed in power, and few analysts expect any real reform. ''The party is fundamentally conservative,'' says Philippe Moreau Defarges, a professor at Paris's Institut de Sciences Politique. ''It is made up of bureaucrats who want to keep their positions and who are scared of changing.''
Few expect the Communists to be able to revive themselves. Not long ago, the Communists could have backed up their threats with strikes led by their large union, the Confederation General du Travail (CGT). Today, the working class is battered and sullen.
The decision to leave the government again makes the Communists a natural refuge for working-class voters upset with economic austerity, analysts say. But this may only stem the party's decline. Communist support after the break is estimated at 12 to 15 percent.
Instead, the consensus is that the decline will continue. Again, a comparison with the Italian Communists best illustrates the French Communists' predicament.
''While the Italians renewed their clientele, the French are relying on the declining base of working-class votes,'' says Moreau Defarges. ''The Italians have been able to attract young voters, immigrants, clerks and other white-collar employees, and intellectuals. In France, there are no more Communist Party intellectuals.''