CHASSIEU, France — A patriotic sea of supporters, waving red, white and blue flags, greeted the newly ascendant presidential hopeful François Fillon this week at a soulless conference center in this suburb of Lyon.

Mr. Fillon described radical Islam as a “totalitarianism like the Nazis” to the cheers of an enthusiastic crowd, adding that France would need Russia’s help to fight it. Catholics, Protestants and Jews “don’t denounce the values of the Republic,” he thundered — unlike the faithful of a certain other religion.

“We’ve got to reduce immigration to its strict minimum,” he said. “Our country is not a sum of communities, it is an identity!”

In a year when nativist politics have become the ticket to electoral victory, Mr. Fillon, 62, a dark-suited, stern-faced former prime minister has managed to successfully ride the same nationalist and xenophobic currents as that have pushed politicians in Britain and the United States to victory.