A new constitution, replacing the 1965 interim document, went into effect April 1977 and was substantially amended in October 1984 and in 1992. It has been amended eight times.
The president, who is both chief of state and head of government, can be elected for no more than two five-year terms by universal adult suffrage. Before the constitutional amendments in 1992, the sole legal party Chama cha Mapinduzi (CCM) nominated the president. Two vice presidents, whom he appointed, assisted him: one was the prime minister and the other was the president of Zanzibar. As of 1995, the president is assisted by a vice president, prime minister, and cabinet. If the president of Tanzania is from Zanzibar, the vice president must be from the mainland and vice-versa.
As of 1995, the 274-seat unicameral national assembly consists of 232 members elected by universal adult suffrage for five-year terms, 36 or 15% of the seats reserved for women nominated by their parties (parties nominate the women members of parliament in proportion to the number of seats they control), and five members from the Zanzibar House of Representatives and the attorney general. Presidential and legislative elections are held concurrently, and in each legislative constituency. All candidates in competing in elections must belong to political parties. The prime minister, who is chosen from the assembly members, heads the assembly. If the president withholds his assent from a bill passed by the assembly, it does not become a law unless the assembly passes it again by a two-thirds majority. The president may dissolve the assembly and call for new presidential and legislative elections if he refuses to assent to a law passed by such a majority within 32 days of its passage.
The Revolutionary Council of Zanzibar, which held power on the islands since 1964, adopted a separate constitution in October 1979, which it replaced in January 1984. The new constitution provides for a popularly elected president and a 75-member Council of Representatives, 50 of whom are popularly elected and 25 appointed. The government of Zanzibar has exclusive jurisdiction over internal matters, including immigration, finances, and economic policy. Since the 1990s, a trend toward greater autonomy for Zanzibar has been the basis of political tension with the mainland.
The Articles of Union and Acts of Union of 1964 provided for two governments: the union government, which also handled mainland issues, and the Zanzibar Government, which dealt with nonunion matters pertaining to Zanzibar. The Tanganyikan Constitution of 1962 was amended to accommodate the two government arrangement, which has remained in place ever since. However, the two-government system has been criticized as favoring Zanzibar because there is no separate government for the mainland. Moreover, Zanzibar's representation in parliament is considered to be disproportionate to its small population. In August 1993, following Zanzibar's attempt to join the OIC in violation of the constitution, the National Assembly adopted a resolution that provided for the possibility of setting up a mainland or Tanganyikan government to parallel that of Zanzibar. The issue of a federated system with three governments has remained a bone of contention between CCM and the opposition parties.
Renegotiation of the Union pact was the key issue of the 1995 elections, the first contested elections on Tanzania in 20 years. Although the former ruling party emerged from those elections with the Zanzibar presidency and a majority in the House of Representatives, the secessionist movement remained strong on the islands. The Zanzibar government established its own department of revenue and foreign affairs.
In February 2000 the Zanzibar CCM and the mainland CCM factions clashed over a constitutional amendment that would have allowed Zanzibar's President Salmin Amour to seek a third term. CCM's National Executive Committee postponed consideration of the issue until after the 2000 elections, effectively blocking Amour's bid. On 29 October 2000, Zanzibar elected Amani Abeid Karume president, and Benjamin Mpaka was returned president of the Tanzanian republic.