A strange map emerged yesterday in the second round of the French presidential election. On the face of it, the incumbent centrist president, Emmanuel Macron, defeated his far-right challenger, Marine Le Pen, by 58.5 percent of the vote against 41.5 percent. However, the closer one looks at the picture, the more intriguing the pattern.

One can hardly speak of a Le Pen underachievement. The daughter of the founder of the National Front actually expanded by eight points her showing from the 33.9 percent of the vote she had garnered in 2017. She led in 28 départements, and in more than 50 percent of all communes nationwide. Once confined to Northern France and Provence, this time she penetrated Eastern France or Occitania, and overcame Corsica. 

Ms. Le Pen’s most consequential advance took place in the far flung French overseas territories, the global population of which is more than 2.7 million : Saint-Pierre and Miquelon in the Northern Atlantic; Guadeloupe and Martinique in the Caribbean; Guyane in South America; La Réunion and Mayotte in the Indian Ocean; New Caledonia, Wallis and / Futuna, and French Polynesia in the Pacific. 

While they are just as French as Metropolitan France in constitutional and legal terms, these territories are different in terms of race, ethnicity, and religion. Afro-French communities predominate in the Caribbean, and Melanesian or Polynesian groups in the Pacific. La Réunion is a melting pot of Europeans, Africans, and Indians. As for Mayotte, it is African and Muslim.

One would have expected these regions to reject a “Fascist” Marine Le Pen. That used to be the case with her father, Jean-Marie Le Pen. In 1987, large-scale demonstrations prevented him from even landing at Lamentin International Airport in Martinique, and then at Pointe-à-Pitre International Airport in Guadeloupe, 117 miles away. Ten years later, in 1997, he ran into similar difficulties at Lamentin, again. 

Yesterday, however, the younger Le Pen swept most of Overseas France: 69.6 percent of the vote in Guadeloupe, 60.9 percent in Martinique, 60.7 percent in Guyane, as well as 59.6 percent in La Réunion and 59.1 percent in Mayotte. The only overseas territories that voted Macron were New Caledonia and Polynesia. 

That’s a stunning reversal. One explanation is that Marine Le Pen, who succeeded her father in 2011, departed from his original far-right agenda and transformed the National Front — renamed National Rally — into a more inclusive, nonracist populist party. If that allowed her to make significant inroads in the Western Atlantic and the Indian Ocean in the first round, it was not enough to carry the second round.

In the first round, on April 10, four of these five regions came out as left-wing strongholds. Jean-Luc Mélenchon, the far-left champion, garnered 56.2 percent of the vote in Guadeloupe, 53.1 percent in Martinique, 50.5 percent in Guyane, 40.3 percent in La Réunion. Whereas Ms. Le Pen got respectively 17.9 percent, 13.4 percent, 17.2 percent, and 24.7 percent. The only overseas place where she came ahead of Monsieur Melenchon was Mayotte.

One must then conclude that Mr. Melenchon’s overseas voters switched in large numbers to Ms. Le Pen in the second round. And the same holds true of many constituencies in Metropolitan France — especially in small and middle-size communes. While there are many places where the far left joined forces with Monsieur Macron or abstained rather than supported Ms. Le Pen (for instance Greater Paris), a sizable leftist vote in the first round was often a prerequisite for a Le Pen surge in the second round. 

Conversely, one may surmise that many Le Pen voters would have been ready to support Monsieur Melenchon against President Macron, in the case he, rather than her, would have been qualified for the second round. What is remarkable here is that this was not so much the result of party strategies than of party sociologies.

Ms. Le Pen’s National Rally, Monsieur Melenchon’s Popular Union, and such lesser players as Eric Zemmour’s Reconquest Party, Yannick Jadot’s Green Alliance, or Fabien Roussel’s Communist Party compete for what has been described as “peripheral” France — that part of the country outside the main urban centers. They share a common devotion to the post-1945 Welfare State, and a culture of frustration, anger, and suspicion regarding the European Union and an American-led globalization. 

The last dividing line among them is the issue of immigration. It is seen as a deadly threat by Monsieur Zemmour, and as a natural outcome by Monsieur Melenchon. Ms. Le Pen is quietly dropping it from her platform, in line with her new inclusive stand. Now, can this Right-Left convergence last until the National Assembly elections scheduled for June 12 and 19? And provided it can, who will benefit from it? 

In her concession speech, Marine Le Pen described the coming parliamentary ballots as a “third round” that may cut President Macron’s victory to size. Short of a solid majority at the National Assembly, the re-elected president will have to share his extensive powers with a hostile prime minister, something known as “cohabitation.” An OpinionWay poll released today discovered that 63 percent of the French see it as a desirable development. An Ipsos poll says that 56 percent of the French actually want Mr. Macron to lose the June elections.

Monsieur Melenchon boldly casts himself as a potential counter-president designated by a left-wing assembly. Monsieur Zemmour advocates an alternative format — a right-wing assembly dominated by “l’union des droites,” a coalition of all conservatives, from Ms. Le Pen to a vestigial classic Right. On the one hand, Marine Le Pen certainly needs the Zemmour voters (roughly 7 percent of the national vote) to win seats. On the other hand, the columnist turned politician was foolish enough to characterize the April 24 returns as “the eighth defeat of the National Camp associated with the Le Pen name.”

Cohabitation may be ultimately averted, and President Macron spared a lame-duck experience, thanks to the electoral law that provides a seat-by-seat majority ballot for the National Assembly. It is tempting to extrapolate in this respect from the first round’s constituency returns. Since Mr. Macron came out first on April 10 in 256 constituencies out of 566, he would theoretically need 27 additional seats only in order to get a majority — something that could be achieved through some maneuvering between rival opposition candidates or with the help of outgoing conservative members of Parliament.

However, even a June victory might not settle the French political conundrum. If the National Assembly is to the liking of the president, one has to beware of a fourth round played in the street. As during the Yellow Vests crisis between 2018 and 2019.