During the first two decades of the 21st century, the major political parties in both Taiwan (the Democratic Progressive Party or DPP and the Kuomintang or KMT) and the United States (Democrats and Republicans) became increasingly polarized in bitter political conflict. In Taiwan, this polarization centered on the strongly inter-linked issues of national identity and cross-Strait relations (Clark and Tan, 2012; Copper, 2016; Fell, 2005, 2018; Makeham and Hsiau, 2005; Rigger, 2011; Wachman, 1994), while in the U.S. the two major parties became polarized on a wide array of economic, cultural, and security issues (Abramowitz, 2010, 2011; Black and Black, 2007; Brewer and Stonecash, 2006; Brownstein, 2007; Layman, Carsey, Green, Herrera, and Cooperman, 2010; Stonecash, Brewer, and Mariani, 2003). In both countries, however, the sharp and vicious polarization of the political elites did not seemingly reflect a similar polarization in the electorate. This situation seemingly challenges the prominent Downsian theory that party positions should reflect the distribution of public opinion based on the assumption that the parties will seek to maximize their vote totals (Downs, 1957). This paper explores this seeming paradox. The first section sketches the basic theoretical model; the second provides an overview of the growing polarization in American and Taiwanese politics; and the third presents survey data from these two countries that cast considerable doubt on whether citizen public opinion is the driving force behind political polarization. The conclusion then seeks to adduce an explanation for why rational politicians would pursue policies that appear to be irrational for their presumed goals of maximizing electoral support and winning office and argues that the observed trends suggest that the “catch-all parties” that evolved during the post World War II era may be now deteriorating under new political conditions.