PARIS — France’s National Rally surged into the lead in the first round of legislative elections, according to results released early Monday, bringing the far-right party to the brink of power and dealing a major blow to President Macron’s centrists in an election that could set the country, and Europe, on a starkly different course.

The results confirmed polling that showed the party — once shunned by the mainstream — is no longer taboo, confined to the fringes of French politics. 

There remains another torrid week of campaigning before the decisive final voting Sunday, and whether the National Rally will be able to win an outright majority and form France’s first far-right government since World War II remains uncertain.

Marked by high turnout of nearly 68 percent that reflected the high stakes, voters handed the Marine Le Pen’s National Rally a strong lead, with about 33 percent of the vote. 

The number includes the votes from a group of conservative candidates of The Republicans party who had allied with the far-right party in the first round. 

The New Popular Front, a leftist alliance, finished second with about 28 percent. The president’s centrist group came third with around 20 percent, according to figures released by the Interior Ministry.

When Mr. Macron dissolved the National Assembly on June 9, after a stinging defeat at the hands of the National Rally in French voting for the European Parliament, the deeply unpopular and weakened president gambled that his rivals wouldn’t repeat that success when the country’s own fate was in the balance.

He and his allies, as well as politicians on the left, are still hoping they can head off an outright win by the National Rally, and horse-trading began Monday, with some efforts to block far-right candidates taking shape. 

The leftist coalition said it would withdraw its candidates in districts where they arrived in third position in order to support other politicians opposed to the far right. Mr. Macron’s centrist alliance also said some of its candidates would step down before the runoff.

In Sunday’s voting, 78 of the National Assembly’s 577 seats were won outright, by candidates who got more than 50 percent of the vote in their district, according to French newspaper Liberation’s analysis of the Interior Ministry data. Of those, 38 were from the National Rally, including Madame Le Pen herself.

That triumph provided an additional boost for Europe’s right as Viktor Orbán’s Hungary takes over the European Union’s rotating presidency for six months.

To underline her party’s triumph, Madame Le Pen said that National Rally lawmakers would meet at the parliament on Monday and symbolically claim their seats.

Addressing a jubilant crowd waving French tricolor flags of blue, white and red, Madame Le Pen called on her supporters and voters who didn’t back her party in the first round to push it over the line and give it a commanding legislative majority. 

That scenario would make the party’s young leader, Jordan Bardella, prime minister — and force him and and Mr. Macron into an awkward power-sharing arrangement.

Mr. Macron, first elected in 2017, has said he will not step down before his second term expires in 2027.

“The French have almost wiped out the ‘Macronist’ bloc,” Madame Le Pen said Sunday night. The results, she added, showed voters’ “willingness to turn the page after 7 years of contemptuous and corrosive power.”