"Two party state" as in a government where politics are bifurcated. In a one party state, a citizen's voting history isn't informative whatsoever about their beliefs. In a direct democracy, their votes give you a complete map of the positions on any issue that came up. In the US, we only know that an R voter prefers the entire set of R policies over the entire set of D policies. Maybe they're pro-taxes, pro-welfare, anti-immigrant, pro-life, and pro-gun, and they weight these positions such that it makes sense to sacrifice the taxes and welfare to get the rest. So, while the party is anti-taxes, everyone who supports it may not be.