PARIS — Call it Droopy's revenge.

For five years, former French Prime Minister François Fillon worked obediently in the shadow of a man who mocked him as a "loser" in private and once berated him publicly as a mere "collaborator." Nobody cared much about Fillon, because he was there to carry out the bidding of Nicolas Sarkozy.

Now Fillon has dealt Sarkozy's career a possibly fatal blow by knocking him out of the conservative primary. The man whose phlegmatic demeanor earned him the nickname "Droopy" pulled off a stunning comeback Sunday to become clear favorite in the primary's final round on November 27. Next May, he may well end up as France's president.

All of a sudden, the world wants to know: Who is this quiet man with bushy eyebrows who has suddenly burst into the limelight?

As Fillon's ideas and policy prescriptions become known, everyone from French voters who backed him on a hunch to policy analysts in Washington may be in for a surprise. Far from being gray, Fillon is a politician who wants radical change — with plans sure to ruffle feathers at home and abroad if he is elected president.

It is in this respect, in calling for a reset of France's international alliances, that Fillon stands apart from Juppé.

He is the most economically liberal candidate the French Right has put forward since Sarkozy's 2007 run, perhaps going back even further. He is a staunch social conservative and practising Catholic who wants to ban adoption for gay couples. Perhaps of greater concern to Washington and other European powers, he is a tireless defender of Russia who blames the West for having provoked Moscow into lashing out against Ukraine.

In short, François Fillon is a man who, if elected, may well carry out his campaign vow to "Bring down the house" — for better or worse.

Thatcher's man in France

But first, there is the man himself. A commonly repeated refrain about 62-year-old Fillon is that he is basically an Englishman who happens to have been born in France. There is some truth to this.

Favoring bespoke suits and expensive Italian shoes, Fillon is a notoriously careful dresser who has moments of British exuberance (see his red socks from Italy's Gammerelli, provider to the Pope). Married to a Welsh woman, he speaks serviceable if strongly accented English, and enjoys the country life, indulging in a "sporting man" obsession for car racing. In public his manner is dry, understated, at times cutting.

But by far the most English thing about Fillon is his economic outlook. A proud admirer of Margaret Thatcher — he told the Financial Times in November he wanted a "showdown" with unions — Fillon wants to inflict the sort of tough love treatment on France that generations of French leaders have avoided due to fear of backlash in the streets and polling stations.

Instead of sugar-coating his ideas, he has taken the opposite tack, warning voters that this is going to hurt.

Only on Europe does Fillon differ with Thatcher. Proposing an overhaul of institutions, he wants to form a eurozone government, integrate EU defense capabilities and beef up protection of exterior borders.

So far, his approach has worked wonders. Fillon may have intuited that France, as some polls have indicated, is in fact desperate for reform. But there is a difference between wanting and getting, especially when he proposes to slash public spending by €100 billion and cull 500,000 civil servant jobs, far more than any of his rivals.

When such hardline proposals, which also include abolishing the 35-hour work week, become better known by the general public, Fillon will face a backlash. It will, almost certainly, be a very broad one that stimulates everyone from socialist Prime Minister Manuel Valls, himself a presidential hopeful, to the statist leader of the National Front party, Marine Le Pen.

"He is Thatcher and Reagan wrapped into one," Bertrand Dutheil de la Rochère, a National Front cadre, said Monday.

Alain Juppé, Fillon's opponent next Sunday, is also primed to attack his Thatcherism. Already, the 71-year-old mayor of Bordeaux has criticized Fillon's economic plan as the "least credible" of any in the conservative field, an absurd wishlist belied by a weak track record of reform during five years under Sarkozy.

Expect Juppé, who is pushing a more cautious agenda, to raise the volume on those attacks before the primary's final round next Sunday.

The Catholics' choice

If Fillon's philo-Thatcherism is well-known, his close ties to elements of France's traditional Catholic Right are less so. Yet they help to explain why Fillon was able to outperform last Sunday, and give a hint of what sort of president he could be.

Unlike Juppé or Sarkozy, Fillon early on voiced support for an anti-gay marriage movement known as la Manif Pour Tous. ("The Rally for All," a deformation of the gay marriage law named "Marriage for All.")

Several aspirants to the presidency, including Sarkozy, have called for dialogue with Russia and made ceremonial visits to see Putin.

This won Fillon the backing of a Catholic current of the Républicains party named Sens Commun ("Common Sense") that provided legions of campaign volunteers in France's traditional western regions. In return, Fillon rewarded his Catholic backers with the most socially conservative agenda of any candidate.

While he does not want to repeal gay marriage, which was voted into law in 2012, he has vowed to ban adoption for gay couples. He is also against medically assisted procreation for female couples and for a universal ban on surrogate mothers. In an open letter to Catholic bishops in October, Fillon said the family was at the "heart" of his political project, vowing to raise public benefits for large families.

"We welcome with great joy François Fillon's clear qualification to the second round of the primary for the Center and the Right," Sens Commun cheered in a statement late Sunday.

Fillon's religious bent also colors the way he thinks and talks about terrorism. The practice of Islam needs to be "controlled" and mosques' financing "rendered transparent" to avoid a "clash of civilizations" on French soil, he told the Catholic website Famille Chrétienne.

In his book "Vaincre le totalitarisme islamique" ("Defeating Islamic Totalitarianism") published in September, Fillon wrote that France was "at war" with radical Islam, and called for tough measures such as taking away convicted terrorists' French nationality. "With the Islamic State we have entered a different universe," he wrote.

In order to defeat ISIL, Fillon argues that France must rid itself of diplomatic taboos — notably the one that stops Paris from forming an alliance with Moscow and Tehran.

For Russia, with love

It is in this respect, in calling for a reset of France's international alliances, that Fillon stands apart from Juppé.

Several aspirants to the presidency, including Sarkozy, have called for dialogue with Russia and made ceremonial visits to see Putin. But none has been as consistently and staunchly pro-Russian as Fillon since he left office in 2012, though he rejects the description that he is Putin's "friend."

Tirelessly, on radio shows and TV panels, Fillon comes to Russia's defense. When Russian-backed troops were sneaking into eastern Ukraine, he argued that it was mostly Russian-speaking and more or less belonged to Moscow. When the West imposed sanctions on Moscow over the annexation of Crimea, he called them "negative" and demanded they be lifted. When Russia went into Syria to assist President Bashar Assad, he brushed off human rights violations and pressed for Europeans to join an alliance with Iran, Syria and Russia against ISIL.

During the U.S. election campaign, some Western officials expressed concern about Donald Trump's warm words for Putin. Not so Fillon, who said: "I do not fear [a Putin-Trump alliance]. I wish for it."

Meanwhile, he has harsh words for NATO, accusing Western powers of provoking Russia by expanding too close to its borders. Denouncing "American imperialism," he wants the euro to become a reserve currency to rival the U.S. dollar and the Japanese yen.