Politics always involves the exchange of resources for votes, but the mechanism differs according to the electoral institution. The principalagent model identifies two necessary conditions for this exchange to be feasible: (1) the opportunity cost of preferential grants is small, and (2) agents receiving these resources play a vital role in helping the principal to win. These conditions were satisfied in the presidential election of 2004, when swing voters were critical in helping the Democratic Progressive Party (DPP) to retain the presidency and limited costs were attached to the resources demanded by legislators elected under the single nontransferable vote (SNTV) system. After 2004, the president no longer exchanged grants for votes at the national level because swing voters could hardly change the result of presidential elections while the opportunity cost of grants was raised by the plurality-tier of the mixed-member majoritarian (MMM) system. Nevertheless, resource allocation still dominates local politics. After MMM was introduced, DPP legislators elected in DPP-led regions distributed the resources that were helpful to consolidating potential supporters; those campaigning in KMT-administered areas, however,attempted to lure swing voters by providing them with extra services—just like what their local heads did.