The election results published on Monday suggested another hurdle for Ms. Le Pen to overcome: a sharp urban-rural divide in the vote, with voters in France’s major cities heavily favoring her rivals. The geography and sociology of her support was similar to Donald J. Trump’s support in the 2016 United States presidential race. She won more départements — between a county and a state in French political geography — than Mr. Macron, and she won the working-class vote. But she did poorly in what French sociologists call “Winner’s France” — urban, employed, well-educated and pro-European. She received less than 5 percent of the vote in Paris, less than 8 percent in Bordeaux and less than 9 percent in Lyon.
Stock markets opened higher on Monday across Europe, a sign that investors were relieved by Mr. Macron’s strong showing. Ms. Le Pen, the head of the National Front, wants France to leave the euro currency zone, a prospect that created unease on international markets in the prelude to the first round of voting.
Few analysts say they expect Ms. Le Pen to win in the second round. Polls released on Monday showed that about 60 percent of voters supported Mr. Macron, compared with less than 40 percent for Ms. Le Pen. A live televised debate between Ms. Le Pen and Mr. Macron is set for May 3.
In Hénin-Beaumont, the northern French city where Ms. Le Pen won 46 percent of the vote and whose National Front mayor is one of her top advisers, even supporters were pessimistic about her chances in the runoff. “It’s a bummer,” said Jean-Louis Devienne, 72. “If people could come here and see how good the National Front has been for our town, they would understand how good it can be for our country.”
On Monday, Ms. Le Pen continued to emphasize the anti-immigrant and anti-globalization views that propelled her into the second round, and she denounced the efforts of the mainstream parties to keep her out of the presidency.
“The old and completely rotten Republican Front, which no one wants, and which the French have pushed away with exceptional violence, is trying to coalesce around Mr. Macron,” Ms. Le Pen said in Rouvroy, a town in the deindustrialized north of France where her message tends to resonate with voters.
Ms. Le Pen also called Mr. Macron “weak” on terrorism, an issue that drew renewed attention days before the first round of voting, when a gunman on the Champs-Élysées, in central Paris, killed a police officer.
President François Hollande is scheduled to pay tribute to the fallen officer at a ceremony on Tuesday. His office said that Mr. Macron and Ms. Le Pen had been invited to the ceremony, and both are expected to attend.
Mr. Macron, who has never held elective office, came first among 11 candidates, with 23.75 percent of the vote. Ms. Le Pen was second, with 21.53 percent, according to final results tallied on Monday by the Interior Ministry.
Mr. Fillon, the center-right candidate who was once seen as the front-runner, before a scandal involving public funds paid to his family, finished third at 19.91 percent. He was followed by Mr. Mélenchon at 19.64 percent, and the Socialist candidate, Benoît Hamon, at 6.35 percent.
The mainstream parties were left struggling to pick up the pieces after their poor showing. On the right, many were quick to blame their candidate, Mr. Fillon, who refused to drop out of the race after the embezzlement scandal.
Mr. Fillon’s Republican party called on Monday for people to vote against Ms. Le Pen, without explicitly encouraging its supporters to vote for Mr. Macron. But many prominent politicians had, with varying degrees of enthusiasm, already directly called on Sunday for voters to support Mr. Macron.
The Socialists and the Republicans will now be looking to elections in June, when French voters will elect the members of the National Assembly, France’s lower and more powerful house of Parliament. Those legislative elections could present a bigger challenge for Mr. Macron than winning the second round of the presidential election. He has vowed to field candidates in all 577 districts. But his political movement is barely a year old, and he is up against the established parties, which are weakened but still have extensive political networks.
Although Mr. Macron is seen as an overwhelming favorite in the second round of the presidential election, he was warned not to take victory for granted and — after he spent Monday night with supporters at a chic restaurant in the wealthy Sixth Arrondissement of Paris — not to celebrate too much, too soon.
Mr. Macron had to avoid making “the same mistake as Hillary Clinton,” the newspaper Le Monde wrote in an editorial on Monday, arguing that Mrs. Clinton had not sufficiently addressed the popularity of her opponent Bernie Sanders in the Democratic Party primaries.