French Socialists salvaged a satisfactory result from a looming electoral disaster in the second round of nationwide municipal elections Sunday. Still, the opposition, rallying around Paris Mayor Jacques Chirac and his neo-Gaullist Rally for the Republic party, took 31 large town halls away from the government, making it plain that the government's 1981 mandate was no blank check for radical reform.
Though President Francois Mitterrand's Socialist Party weathered the voting in fairly good shape, the electorate moved to the center, inflicting the communists with sharp losses.
Voters who had abstained the week before in the first round of the voting swept Mr. Mitterrand's Socialist-Communist alliance to important victories. In all, the left received just more than 50 percent of the total votes cast, and kept control of a majority of the nation's 220 largest cities.
''Last Sunday's setback has been corrected,'' said Lionel Jospin, Socialist Party first secretary. But he added that the vote signalled ''a warning'' to the government that its future policies must be ''more coherent and more realistic.''
Since change is not mandatory at least until legislative elections in 1986, and since President Mitterrand himself has maintained a ''de Gaulle, marble-like'' silence about the elections, it is unclear how this desire to be more realistic will translate into concrete action.
Analysts here are saying there will probably be no sharp alteration of the President's current austerity drive to bring down inflation and the yawning trade deficit. The need for austerity is especially acute now because Helmut Kohl's victory in West Germany has increased pressure on the wobbly franc.
Any policy shift, then, is likely to be toward tightening price and wage restrictions and accepting a rise of unemployment.
To offset these tough measures, analysts think Mr. Mitterrand will take actions to deal with such issues as law and order and immigration, which figured prominently in the local campaign. This could include trying to erase the impression of incoherence of the present unwieldy government of some 44 ministers with a smaller, ''inner'' cabinet.
For the moment, the Socialists have been given a reprieve. They had hoped to suffer only a minor jab in the local voting, but after the first round March 6, they were facing a potential rout. Their share of the vote that day was six percentage points below their score in the 1977 local elections.
The defeat was widely attributed to frustration and annoyance with the Socialist's handling of the economy, notably its modest success in reducing inflation and unemployment. It also reflected fears over increasing crime and the number of immigrant workers in large, urban areas.
In large cities such as Marseilles, Roubaix and Grenoble, traditional Socialist strongholds, the left's electorate stayed home, sinking the government's candidates; or where no candidate won an absolute majority, forcing them into hazardous runoffs.
After the setbacks, the government frantically mobilized to get its voters out for the second round. Voters who abstained in the first week cast ballots in masses during the second polling. Sunday's turnout of 80 percent of the eligible electorate was a national record for local voting.
But there was some worrying news for the Socialists. First, the voting revitalized the opposition and centered it on one charismatic politician, Paris Mayor Jacques Chirac.
Mr. Chirac scored an overwhelming victory in his race for Paris mayor by winning control of all the city's 20 districts.
Secondly, the decline of the Communist Party continued unabated. The party lost 15 towns, including such strongholds as St. Etienne and Nimes and even some towns in Paris's northern suburbs, the ''red belt.''
The decline in the Communists' fortunes leaves Mitterrand with a tricky political situation. In the long run, he must look for ways of enlarging his majority. The inclination would be to move toward the center, and indeed, feelers to join the government have reportedly been put out toward centrists interested in working with the Socialists.
But embracing some maverick moderate politicians such as Fourth Republic stalwart Edgar Faure and the young, handsome Olivier Stirn would probably force the Communists to leave the government. At the same time, the centrists would not bring in many votes by themselves, certainly less than the Communists who continue to control about 11 percent of the electorate.
The upshot is that Mitterrand will probably not marry the center in the near future. He will merely continue to flirt with it.
And as a result, the essential paradox in modern French politics is likely to remain unsolved: a solid majority of Frenchmen seem to wish for government from the center, while the makeup of the country's political parties continues to give them only a left-right choice.