Prime minister leader, the incoming leader will usually be referred as "prime minister-in-waiting". An example or this situation was in 2016 in the United Kingdom when Theresa May was elected leader of the Conservative Party while David Cameron was still prime minister. Ukraine's constitution (1996) lists the powers, functions and duties of the Prime Minister of Ukraine. Most prime ministers in parliamentary systems are not appointed for a specific term in office and in effect may remain in power through a number of elections and parliaments. For example, Margaret Thatcher was only ever appointed prime minister on "one" occasion, in 1979. She
Prime minister-designate the largest party, in which case (s)he becomes prime minister-designate same as if his/her party had a majority. 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 his/her party has the most seats. In the latter case, the prime minister must win a vote of confidence to remain in office. If (s)he is immediately defeated in the house, the head of state in most Westminster systems is often expected to refuse a request to dissolve the house. The