WHICHEVER WAY the French elections turn out this month, they seem unlikely to lead to any simple or stable new balance of forces. It's quite possible that the Left-the alliance of Socialists and Communists -will come to power. But that isn't the only question. The election is also a test of the French voters' reactions to the present style of slow economic growth in Western Europe, after the long boom. The ballot asks them whether it is time to embark on a drastic revision of the traditional relationships between employers and employees.

The first round of voting, next Sunday, is an elimination heat. The final round, a week later, will depend heavily upon the deals struck among the various parties. President Valery Giscard d'Estaing's center group has an arrangement with the Gaullist right, according to which the weaker candidate in each constituency will withdraw and throw his votes to the stronger. The idea is to present a united front to the Left. There is an off-and-on arrangement of a similar nature between the Communists and the Socialists. The present state of their commitments to each other is impossible for any outsider to describe, and their future effect is beyong prediction. But the cutcome of the election and the character of the next parliament probably depend on whether the two parties of the Left can work together in the run-offs.

Ever since last summer, the Socialists and the Communits have been quarreling savagely with each other over their goals. The source of the trouble is evidently the Communists' fear of being swallowed, or ignored, after the election by the larger Socialist Party. But the curious thing about this six months of very public recrimination is that it does not seem to have affected the Left's standing in the polls.

In past French elections, this kind of polling has proved to be remarkably accurate. The polls currently give a significant lead to the Left. The last national election in France was for president, in 1974, when Mr. Giscard d'Esting beat - by a hair's breadth - Francois Mitterrand, then and now the leader of the their national assembly. But the political climate has shifted over the past four years, and not in President Giscard d'Estaing's favor. The 1974 election was held in the immediate aftermath of the great oil crisis, and the Europeans' wildly disorganized reactions to it. President Pompidou had been ill that winter - he was dying, as it turned out, of cancer. There was a demand in France for a kind of national leadership that Mr. Giscard d'Estaing promised, and there was deep anxiety over the inflation that has surged to a rate of more than 15 per cent a year. Today in France there seems to be no sense of sudden emergency, but rather of things going slowly wrong. The government has succeeded in pulling down the inflation rate, but at a considerable price - the unemployment rate is now well over twice as high as it was during the last election. As in most countries, inflation pulls voters to the right, unemployment to the left.

If the Left wins, sticks together and manages to form a government, the conflict then becomes constitutional. President Giscard d'Estaing's term has three years still to run. It is totally unclear whether he could work with a parliament dominated by the Left and his old rival, Mr. Mitterand. The constitution of the Fifth Republic was custom fitted to Charles de Gaulle, and in the 20 years since it was instituted the patter has been one of a strong president who dominated the premier and the cabinet. The question now is whether that constitution would hold up under the strain of a president and a parliament pulling against each other.

There's a widespread impression in Washington that, even if the Left wins a majority of the seats in this months's voting, it won't necessarily bring Communists into the French government. This speculation suggests, a bit too easily, that President Giscard d'Estaing would strike a bargain with the Socialists to form a Center-Left government leaving the Communists out in the cold. That's possibility, but only a very thin one. It is certainly not likely to happen without a period of long and perilous negotiation and confusion. None of the possible cotcomers, in fact, seems to promise a basis for strong and confident government in France.