Minutes after Socialist François Mitterrand won election as president of France last week, his supporters poured into the Place de la Bastille waving red flags and singing the Internationale. There, leaders of the chronically feuding Socialist and Communist parties took up megaphones to pledge cooperation in writing "a new page in the history of France," while more than 150,000 fellow leftists passed wine bottles and danced in a spring shower, celebrating their capture of the Elysée Palace after 23 years of conservative rule. Said one surprised gendarme: "Not since the Liberation have we seen anything like this."

The object of this outpouring is, ironically, neither a reliably leftist ideologue nor a particularly charismatic leader, but rather a crafty and pragmatic compromiser. During his 37-year political career, Mitterrand, 64, has staked out positions all across the political spectrum, drawing nearly as much fire from the left as from the right. A self-styled "Renaissance man," Mitterrand is a Bette Midler fan and avid ballroom dancer who writes poetry in the attic of his Left Bank townhouse and who would, if given the choice, prefer a long solitary walk in the country to a day on the hustings. "After de Gaulle," wrote his biographer Franz-Olivier Giesbert, "Mitterrand is the most unknowable, most mysterious of political men."

For all the campaign rhetoric and promises (among them: to nationalize 10 major industries, reduce unemployment and raise the minimum wage), no one who knows him well is venturing a forecast of exactly what Mitterrand will do in office. Predictable he is not. The son of a vinegar manufacturer, Mitterrand was born and raised in a devoutly Catholic family in the conservative French countryside, where socialism was less than popular. While getting his law degree at the Sorbonne and later during a brief career in journalism, he espoused the cause of pacifism, but he lost no time joining the fight against Hitler's Germany. During the war he was taken prisoner by the Germans, then escaped and worked briefly with the collaborationist Vichy government, only later to join the Resistance, where he met his wife, Danielle Gouze. In 1946 Mitterrand won a seat in the National Assembly on an explicitly anti-Communist platform, but de Gaulle, for one, was suspicious of the young maverick. "Watch this Mitterrand," he said, adding with tongue in cheek: "At heart he's a Communist."

Even after holding a dozen cabinet positions in the series of shaky coalition governments after the war, Mitterrand remained politically elusive. As Minister for Overseas Territories, for example, he worked to divest France of her colonies—but later took a hard line against the Algerian anti-colonial revolt. In this election year he confounded analysts again with an attack on incumbent Giscard d'Estaing for being too soft on the Soviets after their invasion of Afghanistan—despite his own dependence on Communist votes for victory. Critics have called such apparent turnabouts evidence of opportunism. His friends are more charitable. "For him," says one colleague, "socialism is an ethic rather than an ideology." As Mitterrand himself puts it: "I don't calculate. I feel."

Despite that oft-quoted remark, Mitterrand is not an overtly passionate man. At campaign rallies he seemed almost cold, walking stiffly and shaking hands without even the pretense of enthusiasm. "He is not a cold person," defends one longtime friend, "but he is the kind of man who finds it difficult to make cocktail party conversation."

Before the election he was able to escape that circuit by fleeing on weekends to his country house in southwestern France. There he unwound with wife Danielle, 56, and their two sons, Christophe, 34, a journalist, and Gilbert, 32, a law professor—and passed his days tending his trees, two donkeys and two prized Labradors. "Ah, the useful happiness of long walks in which to breathe and think," he wrote in one of his 11 books of political commentary and reminiscence. "I walk in the forest, and the silence and the space cure me of the malady of the cities." Alas for him, the presidency of France will permit far less time for rest and his literary pursuits. He next takes on the fight over the political complexion of a new parliament. As he said after his election: "Now the real troubles begin." For that his friends count him the poorer. "He loves literature," says one. "When things are not going badly he will talk about nothing but literature. He only talks politics when he is worried."