MARSEILLES, NOV. 20 -- Resentment against Arab immigrants has come out in the open in Marseilles, providing a more broadly accepted platform for the far-right National Front and reviving the demon of race in French politics.

The swift rise of the National Front in this boisterous Mediterranean port has been accompanied by similar but more modest inroads in other French cities, particularly those with large immigrant populations. As a result, the National Front's presidential candidate, Jean-Marie Le Pen, has been able to force the anti-Arab issue into national politics as well, obliging mainstream candidates to deal with it as part of the campaign for next spring's elections.

Opinion polls have been giving Le Pen about 10 percent of the national vote for months. Here in Marseilles, however, the National Front won nearly one-fourth of the vote in the last major election in March 1986.

The front's unexpected strength forced traditional conservative leaders to form an alliance with Le Pen's followers in the Regional Council and sent three of Marseilles' National Front militants to parliament in Paris. At the same time, it converted longstanding mutterings against Arab immigrants into declarations that no longer have to be hidden.

Le Pen and his aides in the national campaign, facing charges of racism, have steered away from overtly anti-Arab appeals. Instead, they have relied on indirection, using such slogans as "France for the French." But Marseilles has become so openly resentful of Arab immigrants that this tactic is unnecessary here.

"The National Front is the only party to call {things} by their proper names," said Jean Roussel, one of the parliament members elected last year. "We say there are too many Arabs in the city."

"They are dirty," he added later in an interview. "They have 12 children, and they raise sheep on the balcony. People don't want them any more. There are too many of them."

Although statistics are approximate, officials have estimated that up to a quarter of Marseilles' 860,000 inhabitants are recent immigrants. Spanish and Portuguese among them have drawn little notice. But North Africans, mainly Moslem Algerians, have changed the landscape of the city.

Around the Canebiere, once Marseilles' equivalent of Fifth Avenue, has grown a network of cheap markets that make the city center look like a casbah. Politically more significant, giant subsidized apartment blocks in the northern suburbs have become the sites of conflict as poor Frenchmen feel overwhelmed by growing numbers of Arabic-speaking foreigners with a penchant for strange music and large families.

"They are like octopuses," said Paul Gargiulo, who recently left his job driving armored cars and switched to a taxi. "They slip into someplace, and then there is another one, and then another one, and pretty soon they are taking over. Marseilles is being submerged by Arabs."

Gargiulo's anger, like that of many Marseilles residents, has a special edge because he was forced to leave Algeria in 1962 after France lost the territory in a war. Frenchmen who fled Algeria make up about 10 percent of the city.

In addition, unemployment is higher in Marseilles than in the rest of France -- 14 percent, compared to 11 percent nationally and 9 percent in Paris. This has created a pool of bitterness and a widespread impression that Arabs are stealing jobs from Frenchmen, local analysts explained.

Many National Front supporters in the workers' suburbs formerly voted Communist, but were disappointed when unemployment remained high under the Socialist-Communist alliance that won the 1981 elections.

In 1981, for example, the Communist Party won 25.8 percent of the vote here and Prime Minister Jacques Chirac's neo-Gaullist Rally for the Republic 12.2 percent. By 1986, the Communist vote had fallen to 13 percent, Chirac had fallen to 7.6 percent and the newcomer National Front took 24 percent.

Mainstream conservative officials have charged that President Francois Mitterrand's Socialist Party helped give the National Front respectability as part of a tactic to split away the far-right edge of Chirac's conservative support.

When the Socialists ran the government, before 1986, they changed the organization of legislative elections to proportional representation. This tended to give small parties increased membership in parliament, and the National Front won 33 seats in 1986 out of a total of 577. Previously, it had none.

Membership in parliament bestowed a legitimacy on the National Front that it had not enjoyed before. A major effort in Le Pen's presidential campaign has been directed at expanding on that legitimacy to shed the party's extremist image.

Le Pen's declaration last September that Nazi gas chambers were only "a matter of detail" in World War II history, which generated charges of anti-Semitism, has blurred the campaign's respectability theme for the time being. Political observers have predicted that his comment likely will discourage broadened support from border-line conservatives but will not affect his bedrock following among Frenchmen fed up with seeing Arabs in their neighborhood.

As the number of Algerians in Marseilles has increased, many immigrants have felt less need to adapt to French ways. This, in turn, has created more resentment.

"The thing to do would be for them to assimilate," said Pierre Soubiac, a banker. "But they can't. They don't want to."