Voters in France went to the polls in droves on Sunday in the final round of snap legislative elections. The results could force President Emmanuel Macron to govern alongside far-right opponents or usher in chronic political instability weeks before the Paris Summer Olympics.

Turnout at midday local time was the highest in over two decades, at about 26.6 percent, the Interior Ministry said. That was much higher than during the previous legislative elections in 2022, when the participation rate at the same time was less than 19 percent.

It was also slightly more than midday turnout for the first round of voting last week, reflecting persistent interest in a vote that will determine the future of Mr. Macron’s second term.

Mr. Macron called the elections for the 577-seat National Assembly, France’s lower and more prominent house of Parliament, last month in a risky gamble that appeared to have largely backfired after the first round of voting last week.

Most polls close at 6 p.m. local time on Sunday, or as late as 8 p.m. in larger cities. Nationwide seat projections by polling institutes, based on preliminary results, are expected just after 8 p.m. Official results will come in throughout the night.

Here is what to watch for.

That will be the key question.

The first round of voting was dominated by the nationalist, anti-immigration National Rally party. An alliance of left-wing parties called the New Popular Front came in a strong second, while Mr. Macron’s party and its allies came in third.