This year marks the death of one of France’s noblest political ideals: the cordon sanitaire. Born in 1987 with the publication of a letter, signed by 122 political figures on the French left, it urged the creation of a “republican barrage” against the rise of the anti-immigrant, anti-European, and antisemitic National Front. For nearly four decades, this call was repeated and heeded not just by the French left but also by the right. This resistance was embodied by Jacques Chirac, the Gaullist prime minister and president, who consistently warned against the temptation of seeking common ground with what he called, in 2002, the “poison of extremism.”

But that was then. What we might describe as the centripetal forces that made the cordon sanitaire have since given way to centrifugal forces that are unmaking it. As the first round of municipal elections made clear last week, these forces are now radiating from the ideological extremes and flattening the mainstream parties that had previously melded to make this barrage.

This year marks the death of one of France’s noblest political ideals: the cordon sanitaire. Born in 1987 with the publication of a letter, signed by 122 political figures on the French left, it urged the creation of a “republican barrage” against the rise of the anti-immigrant, anti-European, and antisemitic National Front. For nearly four decades, this call was repeated and heeded not just by the French left but also by the right. This resistance was embodied by Jacques Chirac, the Gaullist prime minister and president, who consistently warned against the temptation of seeking common ground with what he called, in 2002, the “poison of extremism.”

But that was then. What we might describe as the centripetal forces that made the cordon sanitaire have since given way to centrifugal forces that are unmaking it. As the first round of municipal elections made clear last week, these forces are now radiating from the ideological extremes and flattening the mainstream parties that had previously melded to make this barrage.

This gradual evolution of political forces was made manifest in the summer of 2024, when President Emmanuel Macron dissolved the National Assembly and called for a snap election. This move, meant to strengthen his wobbly parliamentary majority, proved as calamitous as it was impulsive. When the votes were tallied, the center-right coalition led by Macron’s so-called Renaissance party lost its parliamentary plurality. Far from heralding a rebirth of the party’s earlier electoral successes, the legislative election proclaimed its decline.

More critically, though, no single party or coalition could convert Macron’s own goal into a victory. Instead, the National Assembly now encompassed three political blocs—the extreme right-wing National Rally, the Macronist center-right, and a volatile left-wing coalition comprising the Socialists, Greens, Communists, and extreme left-wing France Unbowed—none of which could form a parliamentary majority. The series of governments that have since followed, led by three different center-right prime ministers, have proved largely ineffectual. (In early February, the current government under Prime Minister Sébastien Lecornu, after four months of political deadlock, violated an earlier vow by forcing adoption of a budget without a parliamentary vote.)

This crisis has since metamorphized into something graver, one where the deepening polarization fueled by the nation’s two ideological extremes threatens to fragment even further the traditional parties sandwiched in between. While the National Rally has been classed, since its founding as the National Front in 1972, as a movement on the extreme right—and thus outside the so-called arc républicain—the party at the other extreme, La France Insoumise, or France Unbowed, is more difficult to classify. The party’s leader, Jean-Luc Mélenchon, who founded it in 2016, insists it is part of the traditional left and has a place under the republican arc. Yet Macron’s government has argued that France Unbowed’s parliamentary obstructionism and “communitarian” leanings—i.e., its embrace of ethnic identities rather than the abstract ideals of 1789—renders it anti-republican. (Last month, the Interior Ministry declared that France Unbowed, much to Mélenchon’s displeasure, would be officially identified in the recent municipal elections as a “far left” party.)

The rupture between the traditional center and left and France Unbowed was made final by the recent death of Quentin Deranque. An extreme right-wing and ethnonationalist militant, Deranque died on Feb. 14 from injuries sustained by a group of far-left militants during a street brawl in the southern city of Lyon. Several of those charged with Deranque’s death belong to la Jeune Garde, or Young Guard, a small and self-described anti-fascist militia banned by the government in 2025. Crucially, the group, comprising about 200 members, was founded in 2018 by Raphaël Arnault, a member of France Unbowed who was elected to parliament two years ago.

Once the news broke, Arnault predictably declared on X that he was “disgusted and horrified” by the murder and awaited the results of a full investigation. No less predictably, Mélenchon proved equal to his reputation as an abrasive provocateur. He insisted that the members of la Jeune Garde had been lured into a “trap” set by right-wing thugs. Mélenchon also sought to turn the tables by hammering at a single message: “We are the ones who are being attacked.” Far from being the actors in street violence, he declared, his followers have instead long served as a punching bag for right-wing militias. Finally, he refused to sever his movement’s ties to la Jeune Garde and, only when pressed, reluctantly expressed regret over the incident.

On the one hand, statistics bear out Mélenchon’s claims concerning the incidence of violent acts committed by far-right and far-left groups. As recent work by the researchers Nicolas Lebourg and Xavier Crettiez has revealed, far-right movements in France account for 10 times more victims over the past 40 years than do those on the far left. (To be exact, the police attribute 58 murders to those on the far right, compared to six on the far left.) In 2023, moreover, the then-minister of the interior, the hard-line conservative Gérald Darmanin, announced that the police had discovered and prevented 10 far-right plots to commit violence in recent years, while one such plot occurred on the far left.

There is, however, a rather dismal other hand that happens to be attached to Mélenchon. For months, this oft-described “fiery tribune” has seemed intent on setting fire to a unified left. In effect, Mélenchon is trying to turn the 2027 presidential election into a contest between himself and either Marine Le Pen, the nominal National Rally candidate, or the president of the party, Jordan Bardella. (Le Pen is now appealing a French court’s decision, one that would prevent her from running as a candidate, that found her guilty of misusing European Parliament funds for the National Rally.) Having collapsed the prospect of a coalition stretching from the center-left to far left, Mélenchon believes that he and his party can outduel the National Rally in 2027.

Yet there is little evidence that supports this ambition. While he can successfully sabotage the creation of a unified left-wing front against the National Rally, Mélenchon cannot attract enough voters to advance to the second round, not to mention beat either Bardella or Le Pen. According to an Odoxa poll published in late February, the leaders of the National Rally are credited, respectively, with 35 percent and 33 percent support. They are double-lapping most of the other possible candidates, including Mélenchon, who, with a barely 13 percent favorable rating, is falling behind other potential left-wing candidates and, moreover, is shackled to the highest negative rating at 71 percent.

At the same time, Bardella has so far avoided the political disadvantages of youth—he has committed few faux pas in his meteoric rise to the top—and exploited its advantages. In contrast to the leaders of the mainstream parties, the 30-year-old Bardella, who possesses a nearly preternatural self-confidence, personifies a movement that seeks to move beyond its traditional demographic of older and suburban voters and appeal to Generation Z voters. A recent poll revealed that young voters, once firmly ensconced on the left, are beginning to break for the National Rally. A second poll, moreover, shows that a majority of all voters see Bardella’s youth as a plus rather than a negative.

Last month, the political commentator Françoise Fressoz concluded that Mélenchon had become “the useful idiot of the extreme-right.” Earlier this month, Mélenchon provided irrefutable evidence for Fressoz’s claim. Over the first week of March, Mélenchon not only inveighed against the National Rally, but he also engaged in what Jean-Marie Le Pen, the party’s founder, often practiced: les dérapages. These are the so-called verbal slips, mostly antisemitic, that Le Pen delighted to make, such as his description of the Holocaust as “a detail of World War II.”

Mélenchon, it appears, keeps slipping in the same direction. During a rally in Lyon—the scene of Deranque’s murder—in his signature rhetorical weave, he alighted on the name of Jeffrey Epstein, coming down hard on the last syllable. Alluding to the name’s Jewish connotation, Mélenchon then blurted, “Oh, I wanted to say ‘Epstein,’ sorry, it sounds more Russian, ‘Epsteen.’” To a wave of laughter from the audience, Mélenchon wove, “From now on, you’ll say ‘Epsteen’ instead of ‘Epstein,’ ‘Franckensteen’ instead of ‘Frankenstein.’”

Leaders of every political party condemned Mélenchon’s foray into antisemitic conspiratorialism. Among the first to denounce his jibe was Bardella, who lambasted the rally as a “brutal, chilling meeting with clear fascist overtones.” More remarkably, the leader of the conservative Les Républicains, Bruno Retailleau, had already called for a cordon sanitaire not against the National Rally, but instead against France Unbowed. Mélenchon’s party, Retailleau claimed, had “turned the National Assembly into a battlefield. Verbal violence, after all, carries over into physical violence.”

Nevertheless, Mélenchon recidivated at a rally shortly after in Perpignan. This time, though, it was with the family name of his political nemesis, Raphaël Glucksmann, which he first pronounced as “Glucksmen” before correcting himself by saying “Glucksmann.” The latter immediately called him out, declaring that this “clown who plays with the coded antisemitic phrases of the extreme right wing” had become “our era’s Jean-Marie Le Pen.” The prospect of a left-wing coalition with France Unbowed, Glucksmann concluded, had become null and void.

Though Mélenchon apologized for the remark, the damage was done. The tradition of the republican front is now in hospice if not a hole in the ground. The irony, of course, is that Mélenchon, who has long positioned himself as the most steadfast of opponents to the far right, will instead be remembered as the most unserious of opponents and the one responsible for burying the republican front and bringing the National Rally to power.