Credit…Pool photo by Francois Mori

PARIS — In the course of a visit this past week to Saint-Denis, north of Paris, where the poverty rate is about twice the national average, President Emmanuel Macron donned boxing gloves for a moment to spar with a local. “Go on, hit me,” the young man said, “show me what you got!”

It was a stop late in a long campaign during which Mr. Macron, distracted by his fruitless Russia diplomacy, had largely ignored parts of France affected by high immigration, unemployment and hardship — and had seldom shown a real concern for the economic difficulties that rising inflation and gas prices have brought.

Marine Le Pen, the far-right candidate who has brought her anti-immigrant movement closer to power than at any time in the history of the Fifth Republic, focused on precisely these issues, to considerable effect. On Sunday, a bruising gloves-off battle between Ms. Le Pen and Mr. Macron will come to a head as the French choose their president for a five-year term.

No matter the outcome, the election will have profound consequences well beyond France at a time when the United States and its European allies are locked in a precarious standoff with Russia over its war in Ukraine.

Mr. Macron has tried to engage President Vladimir V. Putin of Russia, but has been a dependable part of a united front against the Kremlin. A victory for Ms. Le Pen, long sympathetic to Moscow and indebted for millions to a Russian bank, would no doubt be a victory for Mr. Putin, handing him his most important ally in his quest to weaken the European Union and divide NATO.

An Ipsos and Sofra Steria poll for the daily newspaper Le Monde, published just before campaigning officially stopped on Friday, showed Mr. Macron leading with 56.5 percent of the vote to Ms. Le Pen’s 43.5 percent. He appears to have widened his lead, possibly decisively, during the two weeks since the first round of voting on April 10.

Credit…Dmitry Kostyukov for The New York Times

Still, the likelihood of a high abstention rate and the reluctance of many of the 7.7 million people who voted for Jean-Luc Mélenchon, the narrowly eliminated hard-left candidate, to switch their vote to Mr. Macron has left lingering uncertainty hanging over the result.

Mr. Mélenchon said “not one vote” for Ms. Le Pen; he did not, however, endorse Mr. Macron, who moved right during his presidency and whose aloof assurance is often perceived as arrogance.

The first round of voting showed how France has eviscerated the center-left and center-right parties that were the chief vehicles of its postwar politics. It has split into three blocs: the hard-line left, an amorphous center gathered around Mr. Macron and the extreme right of Marine Le Pen.

A makeover, involving a quieter tone and a lot of smiling, helped soften Ms. Le Pen’s image, but if the packaging is different, the content is not.

She wants to ban the head scarves widely worn by Muslim women; revise the Constitution through a referendum to establish the idea of national preference for access to employment and social housing; restrict child benefits to French citizens; and deport undocumented migrants. She regularly conflates Islam with violence in a country with the largest Muslim population in Western Europe.

Unlikely to win, but now well within the zone of a potential surprise, Ms. Le Pen is no longer an outlier. She is the new French normal. If Mr. Macron does edge to victory, as polls suggest, he will face a restive, divided country, where hatred of him is not uncommon. The old notion that France is ungovernable may soon be tested again.