With barely a week to go before politically important municipal elections, the latest polls suggest that France's Socialist Party is climbing out of the most severe slump in popularity since it came to power.

The right-wing opposition has flung itself furiously into the campaign, depicting the elections as a nationwide referendum on the government's handling of the economy. They have taken hope from the theory of "Carterization" enunciated by some political commentators--the idea that President Francois Mitterrand's sharp drop in public opinion polls beginning last year forebodes a downward spiral similar to the second half of the Jimmy Carter administration.

The latest opinion polls are confusing, even contradictory. They suggest that more than one in three French voters has not yet decided how to vote March 6, but at least they no longer support the comparison to Carter's fate.

Mitterrand, the polls show, still enjoys a 47 percent approval rating--low by comparison to most French heads of state but at least 20 points higher than Carter at his nadir.

What is more, Mitterrand seems to enjoy greater personal popularity than any of the three principal leaders of the opposition: former president Valery Giscard d'Estaing, former prime minister Raymond Barre, and the neo-Gaullist mayor of Paris, Jacques Chirac.

"The three horsemen of the apocalypse," as they have been scornfully dubbed by the press, have yet to convince the voters that they would run the country any better than the Socialists.

While the local elections are shaping up to something less than the political earthquake some predicted, however, they still could provide an important watershed in Mitterrand's Socialist experiment. Many observers here believe that the Socialists will be forced after the elections to take serious steps to repair the economy, and several important economic decisions have been put on ice during the campaign.

The government was forced in June to abandon its ambitious program of economic expansion, which set off Mitterrand's popularity slide. In a radio debate earlier this week, Finance Minister Jacques Delors hinted that the government was contemplating further austerity measures.

France is seeking to reverse its spiraling foreign trade deficit, which amounted to almost $13 billion last year. The franc has lost a third of its value against the dollar since the Socialists came to power in May 1981.

The current mood of disillusionment with all politicians, of both left and right, helps explain why the opposition's campaign to use the country's economic problems against the Socialists so far has failed to take off. Its main effect appears to be to mobilize Socialist and Communist activists into a poster war with the opposition.

The level of political rhetoric in the campaign is reflected in a poster depicting a stunning bikini-clad blonde in the Mediterranean port of Nice. In the caption, she promised to "remove my top," and, sure enough, the next week the same girl appeared topless.

In the final poster of the series, she appeared nude with the caption: "As promised, after 21 months of Socialism, I have nothing left."

In fact, the poster striptease, paid for by Nice's neo-Gaullist mayor, was not even original. The same gimmick was used to promote a billboard company several years ago.

In January, before the start of the campaign, there was a much-publicized reconciliation between Giscard and Chirac. Relations between the two had been frigid since the 1981 election, which the former president believes he lost partly because Chirac never endorsed his candidacy. This being France, the two men settled their differences over lunches--first in a restaurant and then at Giscard's Paris apartment.

This display of unity on the right encouraged the Socialists and Communists to come up with a joint list of candidates for the first round of the elections. In most of France's 219 cities with populations over 30,000, voters will be faced with a simple choice between right and left. The second, decisive round is on March 13.

Despite the Giscard-Chirac reconciliation, each of the three opposition leaders has attempted to outshine his colleagues. The knowledge that all harbor presidential ambitions has encouraged each to try to set the pace in attacking the government.

Perhaps the most dire warning was sounded by Giscard, who forecast that a Socialist defeat in the local elections, combined with the failure of the government's economic policies, would force Mitterrand to call early general elections. Yet during Giscard's presidency the right lost 60 towns in the 1977 local elections without the president dissolving the National Assembly.

Opposition leaders at one point said they hoped to win back all the towns lost in 1977. More recently, they have scaled down their objectivies, apparently in the hope of making any victory look good.

Observers say that the period after the elections could see a heating-up of several simmering industrial disputes, notably among disaffected auto workers at Renault and Citroen. The Communist Party and the unions have been careful not to stir up trouble prior to the elections for fear of giving a boost to the right.

Almost as important for Mitterrand as the municipal elections will be the West German general election, which takes place the day of the first round of the French elections. According to analysts, a Social Democratic victory in West Germany would probably take some of the pressure off the franc but add to French worries about the outcome of negotiations on intermediate-range nuclear missiles in Europe.

Despite being ideologically more in tune with the German Social Democrats, Mitterrand is closer to Christian Democratic Chancellor Helmut Kohl in supporting the deployment of U.S. cruise and Pershing II missiles in Europe if the U.S.-Soviet negotiations in Geneva fail.