France—and, along with it, Europe and possibly the global economy—are about to enter a new and uncertain era. Socialist François Hollande has defeated French President Nicolas Sarkozy. The margin of victory was 52 percent to 48.

The new guard may not be not quite as scary as Hollande’s left-wing rhetoric during the campaign has led some people to believe. Even before the numbers came in, he was moving to reassure financial markets by reaching out to German Chancellor Angela Merkel. And even among the jubilant crowds at Socialist Party headquarters there was a clear sense that tough times lie ahead.

"We're going to celebrate in a fitting way but also with some humility," said Razzy Hammadi, one of the Socialist Party's rising young leaders. "We're going to have to pull people together." In the background, a giant television screen had just shown Sarkozy's concession speech, calling on the French to recognize Hollande's victory, but not without a certain grudging tone. "I have to tell you," said Hammadi, "president or not, Nicolas Sarkozy remains Nicolas Sarkozy."

The vote, though decisive, is not exactly a mandate. Polls have shown consistently that Sarkozy’s biggest problem was Sarkozy. He could score high on competence and credibility, but just couldn’t make himself sympathique. Hollande won largely because of who he wasn’t.

Sarkozy bet his whole electoral strategy on courting the far right—only to discover that he was hated by many there, too. As he used anti-immigrant rhetoric and advertising to pander to voters who’d backed the National Front’s Marine Le Pen in the first round of voting April 22, he alienated what was left of his support in the center. He also earned Le Pen’s scorn and helped turn her into the rising star of the new opposition. Sarkozy’s own party, the UMP, is now widely expected to fall apart.

So it would be a mistake to think that the results tonight marked an enthusiastic popular embrace of Hollande’s socialist platform, which could be summed up by the good old American epithet “tax and spend.”

Hollande has claimed that the austerity pact negotiated by Sarkozy and Merkel (or “Merkozy,” as the French dubbed them) was so severe that it killed growth and therefore hindered rather than helped recovery. A growing chorus of influential voices, from American Nobel laureate Paul Krugman to European Central Bank President Mario Draghi, have agreed, at least in principle.

But Hollande’s ideas could be put to a concrete test very quickly—like, on Monday—by the financial markets that Hollande described during the campaign as “the enemy.” The elections in Greece, which also took place today, may make the markets even more jittery and speculators more aggressive. And France is going to have to borrow about €180 billion ($240 billion) before the end of the year. Under Sarkozy it already lost its AAA credit rating. If borrowing rates start to climb dramatically, the hope of clawing out of the slump will fade very quickly.

So Hollande’s first move is to try to find a way to come to terms with Merkel or persuade her to come to terms with him. We don’t know how Hollande is going to do that, but his moves in the last few hours suggest something of his strategy and also a significant change in the way the French government will be run under his presidency.

Hollande made it clear during the campaign and especially during his almost three-hour televised debate with Sarkozy last Wednesday that his vision of the French president’s role was not like the hyperactive incumbent’s.

Sarkozy famously, or infamously, wanted to be at the forefront of every major policy, and treated his cabinet members almost as flunkies. So when people grew angry with the government, they inevitably grew angry with him.

Hollande has said he’ll adopt the approach of previous French presidents who tended to step back from the fray of daily administration and let their prime ministers take the heat for unpopular policies. (Both President François Mitterrand and President Jacques Chirac actually wound up having to deal with prime ministers and cabinets from their opposition.)

Socialist Party insiders say the man Hollande will name as prime minister is Jean-Marc Ayrault, a veteran politician who, not insignificantly, is a former professor of German. This morning after Ayrault cast his ballot, he told reporters that Hollande, if he won, would place a call to Merkel this very night. Ayrault will be at the center of the action.

In the days and weeks ahead we’ll also get a clearer idea how Hollande will deal with the United States. He’s already said he will pull the French contingent of troops out of Afghanistan before the end of this year, rather than following the American and NATO plan to wait at least until the end of 2013. Hollande will be inaugurated 10 days from now on May 16. He flies to Camp David for a G8 summit on May 17 and 18, then a NATO summit in Chicago on May 20 and 21. In June, French legislative elections will throw new uncertainty into the mix.

Hollande has won, yes. But when it comes to addressing the enormous problems facing France, there’s not a moment to lose.

With Tracy McNicoll at Socialist Party headquarters in Paris.