For example, in the United Kingdom during the 2007 Labour Party leadership election, Gordon Brown was referred to as the prime minister–designate even before the leadership elections had confirmed him in that position. Common circumstances when this happens include upcoming leadership elections where there is only one candidate and/or a clear majority of eligible voters in the election have pledged to vote for a particular candidate. The media sometimes prematurely refers to someone as a prime minister–designate where the broader term of prime minister-in-waiting would be more suitable. The Australian Electoral Commission, the government authority responsible for the conduct of elections in Australia, notes that "it is usually possible for the prime minister–elect to claim victory on the night of the election". In some countries the role is specifically covered by legislation, in others convention applies before the chosen leader is sworn in. Under the broader definition, many prime ministers-in-waiting never actually become prime minister. Terms such as incoming prime minister and prime minister–in-waiting are also sometimes used, although the latter term is also sometimes used prior to an election for a party leader who is leading in the polls and/or has a meaningful chance of winning, or even more generally at any time between elections in reference to any opposition party leader (regardless of his or her party's perceived electoral prospects) and even for future leadership contenders within the current governing party.
However, it has nonetheless seen common use in the media. The term prime minister–elect is sometimes used as a synonym, but in most circumstances it is technically incorrect: a prime minister is usually appointed by the head of state, and not elected to office by the entire nation, as is the case with some presidential polls. The leader of the largest opposition party therefore could still become prime minister–designate perhaps several weeks after the general election. If they are immediately defeated in the house, the head of state in most Westminster systems is often expected to refuse a request to dissolve the house. In the latter case, the prime minister must win a vote of confidence to remain in office. On the other hand, if a prime minister in such a situation chooses not to resign, the leader of the largest opposition party will not become the prime minister–designate even if their party has the most seats.
Often, especially if they do not have the most seats, prime ministers will not attempt to remain in office and will instead relinquish power in favour of the leader of the largest party, in which case they become prime minister–designate same as if their party had a majority. By law, incumbent prime ministers always have the right to try to win the confidence of the house in a confidence vote.
The situation is more complicated in case of a hung parliament. Typically, the incoming head of government will spend two or three weeks as prime minister–designate before being formally sworn in as prime minister. There is usually no set minimum or maximum amount of time set aside for the transition to take place, but often the incoming head of government will want two or three weeks to put affairs in order and determine who should get cabinet posts, which itself might require more time especially if recounts involving prospective frontbenchers are underway. If another party has won a majority government, the prime minister will formally advise the appointment of that party's leader as the new prime minister.
Invariably, sitting prime ministers who after an election have no reasonable hope of commanding the confidence of parliament will resign rather than face a certain vote of no confidence. In the Westminster system, the head of state or his/her representative has the sole prerogative to appoint a new prime minister upon the resignation, dismissal or death of the incumbent prime minister.