Aso decided to call the bluff of the main oppsition party in his policy address.
◆call the bluff ： （相手がはったりをきかせていると見て）挑戦する、やってみろと開き直る。bluffは「虚勢」「はったり」などの意
LONGMAN's definition
★call sb's bluff ⇒to tell someone to do what they threaten to do, becaude you believe they have no intention of doing it, and you want to prove it