PARIS — Barring an act of God or ISIS, or a massive vote for the mysterious Monsieur Blanc, 39-year-old centrist candidate Emmanuel Macron now looks certain to be the next president of France. He emerged from the one and only one-on-one debate against far-right nationalist-socialistic candidate Marine Le Pen on Wednesday night largely unscathed and indeed, according to instant polls, a clear winner.

If he is elected Sunday, the effect on European and global politics could be enormous: a definitive end to what had seemed a wave of nativism and populism sweeping across the West; a huge setback for Russian President Vladimir Putin’s designs to divide and weaken European (and American) democracies; and a much tougher, more united European Union position as London tries to negotiate Brexit.

Macron, a wunderkind banker and political neophyte who briefly served as economy minister in the current discredited government of President François Hollande, did not, as some of his supporters feared, fall on his face in the debate, even though Le Pen called him “the prostrate candidate” who grovels before international financial interests.

The heiress to the legacy of the National Front party founded by her irascible race-baiting father, Jean-Marie Le Pen, is anti-immigrant, anti-Islam, anti-euro, anti-European Union, anti-American, pro-Trump, and pro-Putin and would like to close France’s borders. A victory for her would turn the post-World War II order upside down—a proposition many frustrated and angry French, especially young ones, have flirted with on the left as well as the right.

Le Pen’s strongest suit with many French voters is her position on Islamist terrorism, which she blends with her party’s traditional hostility to immigrants, especially those from Muslim countries. Her vow to deport immediately any foreigners suspected (not arrested or convicted) of connection with jihadi groups sounds plausible and tough to a nation that has suffered horrific terror attacks in the last two years.

Macron’s policies are hard-line as well, even if less strident. And his riposte in the debate was memorable, calling Le Pen “the high priestess of fear” who would take the country to civil war—which is just what the jihadis want.

Still, it is conceivable a major terrorist attack in the remaining days before the vote might sway the electorate in Le Pen’s favor. (One precedent would be the Madrid bombings in 2004, which resulted in a stunning upset for the incumbent Spanish prime minister.)

On questions of economic nationalism, Le Pen repeatedly fell short as Macron, a policy wonk, demanded specifics that she was hard pressed to deliver. Her key pitch to withdraw from the common currency, for instance, became a muddle of francs and ecus and euros that might have evoked nostalgia in some, but provoked a sense of incompetence and chaos among others.

When Le Pen felt herself stumbling, she tried to goad Macron, laughing at him, shaking her head, and tossing out thinly veiled insults and allusions to his private life. At one point she accused him of “playing student and professor,” a smug reference to the fact he married his high-school drama teacher, who is 24 years older than he is. (Yes, there are some amorous anomalies floating around Macron, but this is France: His wife is very attractive, he jokes about his rumored homosexual liaisons—which the Russian press wrote about at length but without substantiation—and few people care.)

Indeed, Le Pen’s Trumpian penchant for nastiness, which plays well with her traditional base, served her very poorly in the debate. The French polling service Elabe, questioning more than 1,000 respondents online immediately after the two-and-a-half-hour verbal slugfest, concluded 63 percent thought Macron more convincing, compared with 34 percent for Le Pen.

This roughly parallels what the polls have shown as the likely outcome of Sunday’s vote, which Macron has been favored to win by a 60-40 margin. Days earlier, one Macron adviser told The Daily Beast flatly, if privately, “it’s decided.”

But another member of Macron’s team, Laurence Haïm, makes the point that it’s not enough for this man with a year-old “movement” called En Marche! (Onward), but no organized political party, to defeat Le Pen with 50 percent of the vote plus one vote. “I think the goal for us is to make sure we massively defeat her,” Haïm told me after the first round on April 23, when Macron and Le Pen emerged from a field of 11 candidates with only a few percentage points separating them as finalists.

The French legislative elections are coming in mid-June. Without the momentum of a huge popular mandate, Macron may have big problems drawing enough supporters from the traditional parties of left and right, the Socialists and Les Républicains, to cobble together a majority.

And that mandate may be very hard to come by. One recent poll shows that 41 percent of those who voted for Macron in April did so by default. Many supporters of the two candidates who nearly tied for third place in the first round—former center-right Prime Minister François Fillon, a darling of conservative Catholics and moneyed interests who espoused “Thatcherite” economics, and far-left former Trotskyite Jean-Luc Mélenchon—remain bitterly disappointed and intensely hostile to both candidates.

While most see Le Pen as utterly unacceptable—a fascist or, as one snobby Fillon supporter put it, “a fishwife”—they well and truly hate Macron, regarding him as nothing more than a front for the failed and phenomenally unpopular Socialist Party establishment.

As a result, among the almost 20 percent of voters who say they are undecided, many may abstain or drop blank ballot papers into the urns on Sunday, in which case there would be three candidates: Macron, Le Pen, and Monsieur Blanc, as we might call him. The latter might not win, but there remains a slim chance he could tilt the final count in Le Pen’s favor.

“It’s not a done deal until the deal is done,” as Macron spokeswoman Laurence Haïm told me. But in the debate last night, as we’d say in vernacular American, Macron done good.