Taiwan has adopted a form of Mixed-Member Majoritarian (MMM) system for the Legislative Yuan (parliament) elections since 2008. Among the total 113 seats, 73 seats are elected from single member districts, 34 seats are elected via proportional party lists, and six seats are reserved for two aboriginal districts. As the new electoral system has a high proportion of single member districts (SMD: 64.6%), it tends to favour a two-party competition asserted by the the Duverger's Law. In order to obtain a majority in the parliament, it is important for the two major parties, the Kuomington (KNIT) and the Democratic Progressive Party (DPP), to select electable candidates who can compete in those normally one-on-one single member districts. This paper analyzes how the two major parties faced the challenge brought by the new electoral system. Specifically, it focuses on why and how both the KMT and DPP adopted a new candidate selection mechanism - namely, the polling primary, in order to strengthen/maintain their competitiveness under the current electoral system. We argue that the new candidate selection mechanism developed by the two major parties could be the best way for them to not only reconcile their intra-party competitions for nomination, but also help them choose electable candidates in the hope of winning the election. In short, the two major parties in Taiwan may soon become a truly election machine.