To assess interparty completion in democratic politics, Dalton (2008) constructed the “party polarization index” based on a left-right ideology. The partisan divide between the pan-Blue and pan-Green camps in Taiwan has been sharp and acute since the 1990s.  This observed reality contradicts the stable and modest prediction based on Dalton’s index. To explain the difference, it is hypothesized that public opinion in Taiwan rests not on a left-right ideological continuum but on the issue of independence versus unification.