formateur

Formateur is the term, notably in Dutch and French, for the politician who is appointed by the Head of State to lead the 'formation' of a government, which is not a mere formality in countries without a de facto two party-system, as proportional representation often means no single party has a majority (and thus can in fact choose the head of government, or traditionally simply sees its leader installed, as in Britain), so a coalition must be forged. In a constitutional monarchy, this appointment is one of the rare moments when an otherwise powerless Monarch still may play a significant political part. The formateur most often comes from the largest party in the future coalition (while an even larger party may remain in the opposition) and generally becomes the new Head of government if his formation succeeds.
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adj. formative, giving form, constructive

n. formative, former

n. one who has to form a new government