Whatever else happens in France's legislative elections next week, it is safe to predict that Pascal Arrighi will end up as a deputy in the National Assembly. His political program boils down to cracking down on immigrants and other troublemakers.

The entry of extreme rightists like Arrighi to the French parliament for the first time in three decades has been made possible by the introduction of a new system of proportional representation. But it is also evidence of the sensitivity of immigration as a political issue, particularly in this great Mediterranean seaport, long regarded as France's gateway to North Africa.

Arrighi, 64, represents the National Front, a party that operated on the margins of French political life until a couple of years ago. The front's electoral appeal has been based on loud denunciations of immigration and the high crime rate that immigrants are alleged to have brought with them.

With its turbulent political traditions, high concentration of immigrants in the city center and outlying suburbs, and festering social problems, Marseilles has proved fertile ground for the front. The party won 26.4 percent of the vote in local elections here last year, coming in ahead of the ruling Socialists and the mainstream right-wing opposition in five electoral districts.

"We were the first party to open our eyes and ears to the problems of insecurity and immigration. These were once taboo subjects in France -- but the other parties have now been forced to address them as well," said Arrighi, a Corsican university professor chosen by the National Front to head its list of candidates for the department of Bouches-du-Rhone, which includes Marseilles.

"The National Front campaign is pure political demagoguery," countered Philippe San Marco, the Socialist deputy mayor and the grandson of Italian immigrants. "If there are more immigrants here than elsewhere, it is because Marseilles is a port that faces the Arab world. We are taking action to control immigration -- but this is a democratic country, and we cannot build a Berlin Wall."

Under the new electoral system, in which citizens vote for lists drawn up by political parties rather than individual candidates, the National Front needs only 6 percent of the vote in the Bouches-du-Rhone to win a seat in the assembly. Opinion polls have been predicting that, nationwide, the party could win about 25 seats in the new 577-member assembly.

The passions that have been flowing in the election campaign in Marseilles, where roughly 25 percent of the 700,000 population are foreigners, have reflected rising racial intolerance in France. The debate has revolved around the 2 million or so Arab migrants from the former French colonies in North Africa who arrived here following independence in the early 1960s.

The Arabs have proved more difficult to assimilate into French society than previous waves of immigrants from European countries. Predominantly Moslem, they belong to a different culture and civilization that seems threatening to many French Roman Catholics. Many immigrants, in turn, have complained of being treated like outcasts in their adopted country.

Fears of a threat to France's national identity surfaced last year in a controversial magazine piece in Le Figaro, a right-wing newspaper. Headlined "Will we still be French in 30 years?" the article predicted that non-Europeans of mostly Islamic faith would account for a quarter of France's population by the year 2015. The cover showed a bust of Marianne, the symbol of the French Republic, shrouded with a veil like those worn by Arab women.

The Le Figaro piece was denounced by other newspapers and by politicians of left and right. But there is little doubt that it reflected the fear and resentment of a significant portion of French people, particularly in areas of high immigration.

The concentration of immigrants in Marseilles has been symbolized by the transformation by Arab immigrants of a block of streets in the city center leading down to the old port into a neighborhood dubbed "the Casbah" by local residents. North African music floats out of upper windows above Islamic butchers and Algerian restaurants. Newsstands sell Moroccan and Tunisian newspapers. Street conversations are conducted in Arabic as much as in French.

"You'll see, in 30 years, Marseilles will be like Beirut," said Jean Roussel, another National Front candidate likely to be elected on March 16.

Commentators have noted similar eruptions of xenophobia during previous periods of high immigration, notably in the 1930s.