LIKE a wife trapped in an unhappy marriage of convenience, the island of Zanzibar has mourned for its independence ever since it joined with the dominant mainland Tanganyika in 1964. While the union, which created modern-day Tanzania, was agreed to by authorities on both sides, separatist and nationalist sentiment still persists. With the approach of Tanzania's first multiparty elections this October, calls for greater autonomy are growing louder. Diplomats say that Tanzania, already overwhelmed by tens, if not hundreds of thousands of refugees from neighboring Rwanda and Burundi, can ill-afford a conflict within its own borders. Some worry that the region cannot withstand any further instability. Hopes are being pinned on Tanzania to carry out a peaceful transition to democracy. Its own world But Zanzibar, just one hour by boat off the mainland, seems like a distinct world. The local government has its own president and Cabinet, albeit with limited powers. Many of the 600,000 people live on two islands - Unguja and Pemba - and feel more aligned to the Arab world than Africa. Veiled women walk the ancient cobbled streets. Muezzin call the faithful to prayer several times a day, the calls resounding over the old slave markets and squares. Zanzibar's Muslim-dominated culture is similar to that of the Persian and Arab traders who passed through this former spice and slaving center. Zanzibaris, having lived over centuries under various colonizers, including Britain and the Gulf state of Oman, want a greater say in their own affairs. ''The view here is that the mainland authority wants to absorb Zanzibar,'' says Haroud Othman, a Zanzibari academic who heads a group of independent electoral observers. ''[But] this place is ... a hodgepodge of civilizations which intermingled for centuries.'' The elections are expected to be most hotly contested in Zanzibar. The Chama Cha Mapinduzi (CCM) or Party of the Revolution - a formerly socialist, now free-market party - has ruled Tanzania for three decades. Diplomats expect the opposition Civic United Front (CUF), whose main difference from the ruling party is its insistence on greater autonomy for Zanzibar, to win most of the 350,000 votes here. ''This is a highly emotive issue with the potential for violence,'' says one Western diplomat. Just as nationalist fervor grows in Zanzibar as the elections near, so does anti-Islamic sentiment on the mainland. The government there was irked by Zanzibar's unilateral joining of the Organization of Islamic Conference last year and forced it to withdraw. Considering that Zanzibaris are a minority of Tanzania's total population of 27 million, many mainlanders resent the island's heavy representation in the government. They argue that since the collapse of world prices of cloves - Zanzibar's main export - its contribution to the national economy has fallen drastically. Zanzibaris, in turn, say they feel robbed of their rights as a separate state. Many resent the socialist experiments imposed by the mainland, which shrunk Zanzibar's economy from one of Africa's richest in the 1960s to one of its poorest today. They bitterly cite political repression by the CCM, which jailed Zanzibari activists. ''The foremost issue for Zanzibaris is their destiny in the union,'' says Seif Sharif Hamad, CUF's vice chairman, who is running for the Zanzibar presidency. ''Zanzibar was a nation-state which got its independence as a member of the [British] Commonwealth. At the drop of a pin, the statehood of the people of Zanzibar was removed in one minute, without their being consulted,'' Mr. Hamad says. The way has been fraught with violence, including the assassination of Zanzibar President Sheik Abeid Karume in 1972. Violence could easily flare again, say the CUF supporters who meet daily in the main town's Jaw Corner Square to discuss tactics. CUF temporarily called a boycott of voter registration, claiming that thousands of registration cards had been deliberately tampered with since the process began on Aug. 7. The Electoral Commission blamed the mistakes on logistical teething problems. Many Zanzibaris want all-out independence. Hamad says this would not be feasible for the impoverished islands. His CUF instead argues for greater fiscal control and the establishment of three governments - Tanganyika, Zanzibar, and the union. In contrast, the CCM wants the status quo. ''We are for the union 100 percent,'' says Deputy Secretary General Ali Ameir Mohamed. Many hope that bloodshed will be avoided. ''We have to live very cordially, we cannot afford to have an angry giant. We're staying together not out of love, but out of need,'' Hamad says.