The issues under debate in this year’s French presidential election are broad and varied: terrorism and trade, the retirement age and social security, the legacy of France in Algeria and the future of France in Europe. But in truth, only one issue really matters: Can the heady cocktail of fear-mongering, nationalism, nostalgia, resentment, pro-Russian foreign policy and big-government economics — a philosophy that is described, unsatisfyingly, as “far right” or “populist,” that takes a particularly virulent online form and that has contributed to recent electoral victories in the United States and Britain — be defeated in a major Western country? And if so, how?

At least until scandal began to damage his campaign, François Fillon, the candidate of the center-right Republican party, offered what looked like the safest formula: steal the populist issues from the “far right” — Marine Le Pen’s National Front — and make them mainstream. In choosing this strategy, he was emulating Theresa May, the conservative British prime minister who has defeated the upstart U.K. Independence Party by announcing she will leave all European trade structures (as UKIP would have done) and make immigration control her priority (as UKIP does already).

Fillon’s version is slightly different — he has called for a halt to immigration from outside Europe, tougher borders and tougher language on assimilation of French Muslims — but the idea is the same. Like Le Pen, whose campaign has been funded with Russian money, he speaks of friendship with Russia. He talks openly about his Catholicism in a bid to lure France’s “family values” voters away from Le Pen, too. But alas, it seems that Fillon’s version of family values included putting his wife and sons on the state payroll , a story that just won’t go away.

That leaves the contest in the hands of Emmanuel Macron, a 39-year-old social and economic liberal whose strategy is quite different. It’s been clear for some time that the old left-right split in European politics doesn’t reflect real social divisions, and that the new fault lines are better described as “integrationist” vs. “nationalist,” or, more bluntly, “open” vs. “closed.” But although the “closed” voices — parties such as Le Pen’s National Front or UKIP — are long established, Macron is the first major European politician to attract mass support by putting up a vigorous, active and angry defense of “open.” “I defend Europe,” he told a British journalist. “If you are shy, you are dead.”

His strategy, so far, has been built on defiance of ideological stereotypes. Macron has a background in banking but speaks about “collective solidarity.” He served as a minister in a Socialist government but has said that “honesty compels me to say that I am not a socialist.” Instead of a traditional political party he has his own movement, En Marche — a rough translation might be “Forward” — that he launched, to widespread skepticism, in 2016. He has invited U.S. scientists, especially those working on climate change and clean energy, to come live in France. He wants to roll out the red carpet for British academics and businessmen marginalized by May’s retreat from Europe, too.

He also attracts enemies. Because his victory would strengthen both the European Union and NATO, Macron’s campaign has naturally attracted the attention of those who want to destroy them. Both WikiLeaks (which claims to have “secret documents” on all the candidates) and the Russian propaganda channel RT have attempted to show sinister links between Macron and Hillary Clinton. The predictable whispering campaign is conspiratorial (“Macron is part of a secret cabal”), anti-Semitic (“Macron works for the Rothschilds”) and personal (“Macron is gay”). That kind of negative campaigning — based on slurs and hysterical allegations — has worked brilliantly in other countries, and there is plenty of time left for it to succeed in France.

Macron’s success will depend on whether he can withstand the coming smear campaign, and then pull off a trick that has so far eluded his British, Dutch and other counterparts: Unite the center-left and the center-right behind a single banner, and run a campaign that is patriotic as well as “open,” tough on terrorism as well as “integrationist.”

The stakes are high. If he loses, muscular liberalism will disappear from France for a generation. But if he wins, he will have many eager imitators, not only in France but also across the continent and around the world.

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