In the classical model of democracy, governments are responsive to the mass public, making public policies favored by a majority of citizens while respecting the rights of minorities. In the real world, of course, no political system, democratic or otherwise, has ever fully realized this principle of political equality. The focus of this essay is an examination of research on how economic inequalities impact democratic politics. The question has become especially pressing as economic inequality has risen, in some countries quite dramatically, in recent decades. Political inequality may refer to either differential inputs into policymaking processes, in which some actors have more influence than others, or it can refer to policy outputs, in particular those which encourage or sustain income and wealth inequality. In this essay, I review four contemporary theories of political inequality (elite and oligarchic models, power resources theories, globalization models, and participatory inequality models). Each throws light on some aspects of political inequality, but none provides a completely satisfactory account. I conclude with some suggestions for future directions for research.