On French stability, Constitution, and -- an actor in politics

Often contentious, French politicians have gone to new lengths recently to find a controversy. They are asking: If the nation's president comes from one party and the National Assembly is dominated by another party, should the two work together?

Such a situation has never occurred under the Fifth Republic. And political analysts are divided on whether it is workable. During the past month, conservative opposition leaders have engaged in a widely publicized debate over what they should do if they win the next parliamentary elections.

Paris Mayor Jacques Chirac says he would cooperate with Socialist President Francois Mitterrand. But former Prime Minister Raymond Barre refuses.

The Socialists, though, are not yet worrying about a constitutional crisis. After all, the next legislative elections are three years away, in 1986.

Reflections on the Constitution

Even the Socialists are reflecting this month about the Constitution. Twenty-five years ago this month, the Fourth Republic came to an end and the Fifth was officially born.

At the time, the present Socialist Party refused to accept the new Constitution, arguing that it sanctioned an illegitimate seizure of power by Gen. Charles de Gaulle. Francois Mitterrand, a senator, branded the new republic , ''le coup d'etat permanent.''

But almost every other political faction approved, and in a referendum 79 percent voted yes. In its 25 years, the Fifth Republic has continued to be popular because it provided France with a rare measure of political stability. Gone are the almost monthly changes of government during the Third and Fourth Republics, replaced by a strong president who serves for seven years.

Today it is Francois Mitterrand who wields the executive powers that he once criticized. ''The institutions of the Fifth Republic were not made for me,'' he is reported to have said, ''but they fit me very well.''

Instead, it is the conservative opposition that held power for the first 23 years of the Fifth Republic that is calling for constitutional changes. Former President Valery Giscard d'Estaing has just demanded the use of referendums to cover important social issues as well as purely constitutional matters, the reinstitution of a veto power to the now symbolic Senate, and finally, the shortening of the president's term to five years.

None of these changes is likely to be made. When Mr. Giscard d'Estaing was in power, he never wanted his term shortened. Niether does Mr. Mitterrand now, who repeatedly tells visitors his greatest advantage is the ''duration'' provided by the long presidential mandate.

Montand upstages the politicians

While political leaders have been pontificating about all this, they have been upstaged by none other than singer-actor Yves Montand. The newsweekly Le Point proclaimed him ''September's political star'' on its cover.

Mr. Montand has moved into the political limelight by writing newspaper articles, signing petitions, and appearing on radio and television. On each occasion, he has expressed a controversial point of view with eloquence.

In the magazine, he called for stronger French intervention in Chad. In the petition, he called for the defeat of a far-right candidate in mayoral elections for the town of Dreux. But on radio and television, he added that he could not bring himself to vote for the Socialists as long as they continued to be allied with the Communists.

''I would abstain,'' he said. ''I do not want to be associated with those who estimate that the occupation of Afghanistan, the events in Poland, the shooting down of the South Korean jetliner are all just acts.''

Such views come as somthing of a surprise from a man who was once a staunch supporter of the Soviet Union. Only the invasion of Czechoslovakia in 1968 and Alexander Solzhenitsyn's exposure of the gulags (labor camps) in the mid '70s ended his long love affair with communism.

As the press attention shows, Mr. Montand's new political moderation seems to have struck a welcome chord. A poll released this week even said that 17 percent of the population would vote for him if he ran for president.

But with proper respect to his singing and acting talents, 81 percent said they preferred Mr. Montand to keep out of politics and continue his artistic career.