declarer

(noun) the bridge player in contract bridge who wins the bidding and can declare which suit is to be trumps. Synonyms: contractor.

(noun) someone who claims to speak the truth. Synonyms: asserter, affirmer, asseverator, avower. Examples: "A bold asserter." "A declarer of his intentions." "Affirmers of traditional doctrine." "An asseverator of strong convictions." "An avower of his own great intelligence."