Why did the unified government led by Taiwan's president Ma Ying-jeou experience gridlock? In this article, I answer this question by modifying the veto player theory to explain how policies are made in Taiwan's semipresidential system, in which the president can unilaterally appoint a premier who is accountable to the national legislature. Given this constitutional design, the premier represents the president rather than the legislature, so the agenda setter is either the legislature or the president. A veto player model shows that the legislature, as a collective veto player, has the last-mover's advantage when it sets the agenda and that the two executive heads are more likely to be incongruent if a policy has to be deliberated by the legislature. The president sets the agenda only if he can discipline the legislators in his party and the legislature is not allowed to amend an executive proposal. This theory explains why policies involving lawmaking give Taiwan's Legislative Yuan considerable bargaining powers, even to the disadvantage of the president. These theoretical arguments are confirmed by hypothesis-based case studies and can be generalized to study other semipresidential regimes.