“Just watch the interlopers from the world over come and install themselves in our home,” she said. “They want to transform France into a giant squat.”
“But it’s up to the owner to decide who can come in,” Ms. Le Pen continued. “So, our first act will be to restore France’s frontiers.”
The words were red meat to her base of supporters and were intended to shore up her flagging poll numbers as the campaign closes. Polls once showed her at 30 percent, but instead of consolidating her lead, her support fell as doubts about her readiness to govern grew.
Ms. Le Pen is still expected to emerge on Sunday as one of the two finalists in the May 7 runoff, a breakthrough for the far right given that her father’s second-place finish 15 years ago came as a huge shock.
Polls predict a heavy loss for her in the second round, however. A poll conducted for Le Monde and published on Tuesday said she would get only about 30 percent of Mr. Fillon’s voters in the second round — not nearly enough, according to Joël Gombin, a National Front specialist at the University of Picardy Jules Verne, who said she must get more than 50 percent of former-Fillon supporters to have a shot at a final victory.
But Ms. Le Pen is not taking any chances with the first round either. Tough talk on immigrants is what her supporters want from her, and Wednesday night at the Dôme, an immense metal-covered indoor arena in a run-down neighborhood of Marseille set back from the port, they were not disappointed.
As she denounced her opponents on the left as “immigrationists,” men in the stands shouted, coarsely, that they would cut off a certain part of their rivals’ anatomy.
Police officers brandishing automatic weapons guarded the hall — two men were arrested in Marseille on Tuesday and are suspected of preparing an attack to disrupt the election — and Ms. Le Pen eagerly linked immigration to “insecurity,” a favorite theme of hers.
Violent protests by leftist demonstrators have disrupted recent National Front meetings, although ones held on Wednesday were relatively subdued.
Referring to those under surveillance as possible security threats, Ms. Le Pen called France a “hotbed of S-files, that immense army of the shadows who want us to live in terror.”
She unleashed volleys of fearful warnings about her country’s transformation — in her telling — by an immigrant wave.
“The third-world demographic push is accelerating,” she warned. “There is a migratory submersion which is sweeping everything before it.”
“Will we be able to live much longer as French people in France, while entire neighborhoods are being transformed?” Ms. Le Pen asked. “It is right for us not to want our country transformed into a mere corridor, a giant railway station.”
Areas around Marseille and other parts of southern France have large immigrant populations from North Africa. Ms. Le Pen’s words found ready takers in the stands, where supporters spoke with dismay and anger at seeing their hometowns, in their telling, made unrecognizable by the presence of immigrants.
“It is absolutely frightful. I’ve never seen so many burqas,” said Christiane Guille, a nurse from Salon-de-Provence, referring to the head-to-foot robe worn by some Muslim women. “Frightful. And it’s getting worse and worse. It’s like a cult. I know some who have converted. You see them indoctrinated, the passage from one civilization to another.”
“For me, there is a huge replacement going on,” Ms. Guille added, using what has become a stock phrase for people on the far right to describe what they see as France’s transformation. “I cry for my Provence. I feel hatred. By what right do they take over my country?”
Ms. Le Pen’s words on immigrants, she said, “went straight to my heart.”
Odile Ferrero, 60, a retired home health worker, said her town, Aubagne, was “stuffed” with immigrants.
“It’s like whiteflies. They are just everywhere, everywhere,” she said. “And all the little ones, who used to come home with my daughters, they went swimming together — and now they are all wearing the veil.”
“There are some who are good,” she continued. “But then there are others. And now they have more rights than we do.”
Ms. Le Pen has proposed a series of anti-immigration measures, constants in her campaign for months, but with some new ones in the last few days.
She promised a “moratorium” on immigration “as soon as I take office”; an end to family reunifications — the longstanding and divisive policy of allowing into the country family members of immigrant; the expulsion of illegal immigrants, “because it is the law”; the expulsion of “S-files” who are foreigners; and cutting medical help to illegal immigrants.
All of the proposals met with roars of approval.
France had a record number of asylum-seekers last year, 85,700, and about 227,500 foreigners were granted residency permits of some sort, an increase of nearly 5 percent from the preceding year. Ms. Le Pen has spoken of drastically limiting legal immigration to around 10,000 people a year.
“There’s far too much insecurity, as far as immigrants are concerned,” said Francis Scueil, a cheese factory worker from Salon-de-Provence. “They are just not adapted to the French way of life. When you go to the markets, that’s all you see.”
As the buses carrying the National Front supporters pulled away from the Dôme late Wednesday, a group of Muslim women, most wearing head scarves, gathered to look, tentatively leaning forward from under an adjoining highway overpass.
“More and more are coming from the third world, taking advantage of our benefits,” Ms. Le Pen had said at the rally. “It’s a choice of civilization. I will be the president of those French who want to continue living in France as the French do.”