Wang, GuanHow does U.S. foreign policy differ under unified versus divided government? Much of the existing scholarship concentrates on the repercussions of divided government on domestic affairs. Yet, there is little research exploring the influence divided government might have on U.S. foreign policy. My dissertation aims to bridge this gap in literature. My central argument is that U.S. foreign policy garners less attention from politicians and is accorded less agenda space under unified government compared to divided government. This disparity holds important implications in three main areas: the progression of foreign policy bills through legislative processes, the decision to impose sanctions through the United Nations or alternative approaches, and the frequency of change in the policies towards China. Under unified government, the majority party often seizes this opportunity to focus on issues that will bolster their prospects in the next election. Typically, these issues are domestic in nature. Given the limited attention span of politicians and the constraints of institutional agenda, the consideration of foreign policy issues tends to be postponed. By contrast, under divided government, domestic issues negotiations frequently face gridlock. Foreign policy issues, which are more likely to see bipartisan consensus, receive more attention and greater agenda space. Empirically, I analyzed the entire corpus of foreign policy bills in Congress and all sanctions imposed by the U.S. over the last two decades. I also incorporated a wide array of official documents and politicians’ speeches concerning U.S.-China relations. The results show that foreign policy bills are more likely to be considered by the House floor under divided than under unified government, the U.S. is more likely to impose sanctions on a target through the United Nations under divided than under unified government, and Washington is more likely to formulate new policies towards China under divided than under unified government.enDissertationPolitical science