The SLPP dominated Sierra Leone's politics from its foundation in 1951 to 1967, when it lost the 1967 parliamentary election to the APC, led by Siaka Stevens.

The party was in power from 1996 to 2007, when it again lost to the APC, led by Ernest Bai Koroma, in the 2007 presidential election.

This unity did not extend to national politics, as opposing politicians often faced detainment under SLPP rule.

Politically, he attempted to strengthen the position of SLPP elites relative to the chiefs, who had formed the backbone of the party.

Albert also embarked on a policy of Africanisation, which removed some civil servants who favored a colonialistic approach.

Margai may have adopted this strategy in an effort to replace the Creole civil administrators with unqualified members of his Mende tribe.

The subsequent political unrest led to the declaration of martial law and a military coup that took full control of the national government.

The National Reformation Council (NRC), led by Brigadier Andrew Juxon-Smith, was established on 23 March 1967.

Pressure from political elites, trade unions, and university students led to the junta's collapse in November 1970, and Siaka Stevens of the APC became president after the interregnum.

In 1996 SLPP returned to prominence, as its candidate Ahmad Tejan Kabbah won the presidential election, receiving 59.5% of the popular vote in a second round against John Karefa-Smart of the United National People's Party (UNPP).

[16] In the August 2007 election, the SLPP was defeated by the APC in the parliamentary election, winning 43 seats against 59 for the APC; the PMDC, a splinter party founded by Charles Margai, attracted the support of some traditional SLPP voters, winning 10 seats.