By elevating his personality over mere institutions--institutions he devised when he dictated the Fifth Republic's constitution--Charles de Gaulle depoliticized French politics. Francois Mitterrand, the first socialist president of the Fifth Republic, is, in his way, as aloof as De Gaulle. He has held only one proper press conference, and regularly retreats to seclusion in the country.

But De Gaulle's aloofness was anti- political mystification, part of his program for turning France into a sanatorium for itself after the disaster of 1940-44. Mitterrand's near-invisibility is part of a program for rehabilitating politics by putting presidential personality in abeyance. The presidential powers (including a seven-year term) conferred by the Fifth Republic's constitution, combined with a socialist majority in parliament, make Mitterrand's government the most powerful government in postwar France.

Around 1965, Mitterrand experienced a kind of epiphany, suddenly understanding that "all fundamental change comes through conquest of state power." Statism is as French as cognac, but Mitterrand's is grounded in a poor sense of history.

American history is a history of unprecedented change--social, political, commercial, technological, intellectual-- without supervision by state power. State power has been of secondary, even tertiary, importance to the intellectual and scientific forces that have transformed the 20th century, including France.

Mitterrand has been called a revolutionary manqu,e. Ten years ago he spoke the language of pure leftism, denouncing the "power of money," and all that. He recently warned about "the revanchist and often provocative side of reactionary forces in the Western world," and wondered, "What inherent difference is there between imperialist ideas according to whether they come from East or West?"

The crumbling of the French left's last dreams about Soviet communism --a crumbling for which Solzhenitsyn deserves considerable credit--has not altered the socialists' assumption that capitalism and communism are "equally" failures. Shortly after becoming president, he sent a message to Castro, proposing cooperation "au service du respect des droits de l'homme."

Mitterrand's alliance with the Communists is a hostile embrace by both sides. The Communists expected an "Italian" outcome, with the socialists losing their rationale and becoming minor partners. Mitterrand gambled that the socialists would gain at the expense of the Communists, and that the withering of Communist strength would diminish middle-class inhibitions on voting for the left. He won.

The marriage between the socialists and Communists is unwarmed by affection and, like many modern marriages, is not expected to endure. Last year, the day Communists were taken into the government, a Mitterrand ally was asked how long they would stay. He said: until after the 1983 municipal elections. The socialists are hostage to the Communists until after those elections, because Communist strength is greatest in those elections.

So perhaps Mitterrand must continue his high-risk policy of domestic reflation and redistribution until then. Otherwise the Communists could jump ship and emerge as the "true defenders of the working class" against a socialist government "doing the work of the right." For now, Mitterrand is in partnership with totalitarians whose leader praises, for example, "the fundamentally humanist nature of the communist (Moscow and Warsaw) approach to recent events in Poland."

At Mitterrand's inaugural luncheon last year, Salvador Allende's widow sat at Mitterrand's side, evidence of the socialists' obsession with Allende's fall. They radically misinterpret that Chilean episode. They think Allende fell because he did not seize the levers of economic power quickly enough, and because he did not maintain sufficiently amicable relations with the United States.

However that may be, Mitterrand has plunged into nationalizations at a reckless pace, and has tried to be selectively agreeably toward the United States. He tries harder to be agreeable than any other Fifth Republic president has done --which is, of course, saying precious little. But he is more genuinely anti-Soviet than Giscard d'Estaing was; he has decided to build a seventh nuclear submarine; and he has increased defense spending more than any NATO member except the United States.

Europeans, and especially socialists, derive from the United States something they value even more than military protection: alibis. They blamed their failures on American inflation until American inflation plummeted; now they blame American interest rates. But Mitterrand's laments about the cost and scarcity of investment capital would be more convincing were he not providing the Soviet Union with so much credit at below-market rates. There is a large discontinuity between Mitterrand's anti-Soviet rhetoric and his policies. But the Reagan administration has long since forfeited the right to act sniffy about that.