France’s left-wing parties surged unexpectedly in nationwide legislative elections on Sunday, denying the nationalist, anti-immigration National Rally party a majority in the lower house of Parliament.

But official results showed that no party or bloc had secured an absolute majority, leaving one of Europe’s largest countries headed for gridlock or political instability.

Here are five takeaways from the election.

There were two big surprises as France voted for a new Parliament in snap elections, neither one foreseen by pundits, pollsters or prognosticators.

The biggest was the triumph of the New Popular Front, a coalition of left-wing parties that is now the dominant force in a bloc of about 190 lawmakers and that has emerged as the lower house’s leading political group.

It was the French left’s most surprising victory since François Mitterrand brought it back from its postwar wilderness, winning the presidency as a Socialist in 1981.

President Emmanuel Macron, backed by much of France’s commentariat, has spent the last seven years proclaiming the left — and especially the Socialists — dead, and its more radical fringes like France Unbowed as dangerous troublemakers. Both won big Sunday.

Jean-Luc Mélenchon, the founder of France Unbowed, which is projected to have won about 75 seats — perhaps over a dozen more than the Socialists — declared that Mr. Macron now had a “duty” to name a prime minister from the left’s coalition, the New Popular Front. He boldly said that he would refuse to “enter into negotiations with the president.”

In Paris, a large, boisterous crowd assembled to celebrate in the mostly working-class neighborhood around the Place de la Bataille-de-Stalingrad on Sunday night.

The two other parties in the New Popular Front are the Greens, which are projected to get about 35 seats, and the Communists, who are projected to get about 10.

The other shocker was the third-place finish of the National Rally and its allies, which had been expected to win the most seats, if not an absolute majority, in the 577-member National Assembly, the more powerful lower house.

The party was already preparing to govern alongside Mr. Macron in what is known as a cohabitation, when the prime minister and the president are on opposing political sides.

Still, the National Rally and its allies did win about 140 seats — more than at any time in its history, which the party was quick to point out.

“The tide is rising,” Marine Le Pen, the party’s longtime leader and perennial presidential candidate, told reporters on Sunday. “It didn’t rise high enough this time, but it’s still rising. And as a result, our victory, in reality, is only delayed.”

But the fundamental mutation predicted before Sunday — that France would become a country of the hard right — did not occur.

And so for all Ms. Le Pen’s bluster, the National Rally’s election night party was glum.

It is still too early to say how voting patterns shifted between the two rounds of voting and how the New Popular Front pulled off its surprise victory. But strategies aimed at preventing the far right from winning by forming a “republican front” appear to have played a big role.

France’s left-wing parties and Mr. Macron’s centrist coalition pulled out over 200 candidates from three-way races in districts where the far right had a chance of clinching a seat. Many voters who abhorred the far right then cast their ballot for whoever was left — even if the candidate was hardly their first choice.

“I never would have voted for France Unbowed under normal circumstances” said Hélène Leguillon, 43, after voting in Le Mans. “We are forced to make a choice that we would not have made otherwise in order to bloc the National Rally.”

The far right argued that the tactic was unfair and that it robbed its voters of a voice.

“Depriving millions of French people of the possibility of seeing their ideas brought to power will never be a viable path for France,” Jordan Bardella, the National Rally president, told supporters in a speech, accusing Mr. Macron and the left of making “dangerous electoral deals.”

Official figures for the final-round turnout were not immediately available on Sunday night, but pollsters projected that it would be about 67 percent, far more than in 2022, when France last held legislative elections. That year, only about 46 percent of registered voters went to the polls for the second round.

The turnout on Sunday is the highest since 1997, reflecting intense interest in a race that had much higher stakes than usual.

France’s legislative elections normally occur just weeks after the presidential race and usually favor the party that has won the presidency. That makes legislative votes less likely to draw in voters, many of whom feel as if the outcome is preordained.

This time, though, voters believed that their ballot could fundamentally alter the course of Mr. Macron’s presidency — and they appear to have been right.

With no party having an absolute majority, and the lower house of Parliament about to be filled by factions that detest one another, it is unclear just exactly how France is to be governed, and by whom.

Mr. Macron has to appoint a prime minister capable of forming a government that the National Assembly’s newly seated lawmakers won’t topple with a no-confidence vote.

There is no clear picture yet of who that might be, and none of the three main blocs — which also have their own internal disagreements — appear ready to work with the others.

“French political culture is not conducive to compromise,” said Samy Benzina, a public law professor at the University of Poitiers.

Mr. Mélenchon is disliked by many in the Socialist Party (and even by some within his own party, who resent the hold he has on it even though he is no longer its formal leader); Mr. Macron’s Renaissance party contains members who resent the president for having called the snap election; and most lawmakers who are not members of the National Rally abhor it.

Mr. Macron himself is a potent generator of anger, as he has proved repeatedly during his seven years as president, although he has already ruled out resigning. The latest survey from the Ifop polling institute, conducted after his decision to call a snap election but before the vote itself, gave him an approval rating of only 26 percent.

Where will France’s next prime minister come from? What legislative sway does Mr. Macron still have? Can he even continue to preside if the lower house is ungovernable?

Stay tuned.

Ségolène Le Stradic contributed reporting from Le Mans, France.

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