One-party dominant state
The one-party dominant state is a system of majority rule where one political party has successively won election victories by a very large majority and is, therefore, the dominant ruling party, which does not have to form coalitions (alliances) with other smaller political parties as a result.
The one-party dominant state differs from a one-party state, because opposition parties against the dominant ruling party are allowed, but have no real chance of gaining power.
Many one-party dominant states are dictatorships where only one party can by law be in control, but some one-party dominant states are real democracies, where there are no limits by law against other parties.
In South Africa, the National Party of South Africa ruled from 1948 to 1994 and imposed apartheid. With the democratization of the country and the election of Nelson Mandela in 1994, African National Congress became the ruling party, winning every election since then.
In one-party dominant states that are dictatorships, the ruling party often stays in power through electoral fraud and gerrymandering, and also by suppressing the opposition who don't accept this for moral reasons, which totally undermines the political legitimacy of the ruling party and the system.