The rise in economic inequality in the United States appeared to be causing congressional ideological polarization—but congressional ideological polarization was also leading to increases in inequality, so causality was a vicious circle. Nolan McCarty, Keith T. Poole, and Howard Rosenthal found in 2007 that inequality exacerbated ideological polarization, and ideological polarization led to policies that further increased inequality. In other words, they found that people with vastly differential wealth had different policy preferences. But ideological differences between Republican and Democratic partisans led to the failure of redistributive policies, thus exacerbating inequality.

Basically, economic inequality leads to elite polarization (at the congress level) that limits the political agenda to policies that do not benefit the public, so that the public can only vote against its interest. This leads to more economic inequality and so forth. There are more layers to it, such as economic inequality creating elites in the private sector and leaving politics to incompetent people that are manipulated by the business elite. My initial description is somewhat simplistic, but essentially the public is cut off from the elite due to economic inequality, leading to political polarization as the only differentiating factor in policy, so that the public can only vote against its interest.