No self-respecting political scientist will accept the cliché that demography is destiny; nevertheless, as a country’s demography changes, if the politics do not change in accord with the circumstances or desires of the new residents, one sees greater and greater strain and even disruption in governance. A crucial question is whether the political effects of native-borns’ anxiety about immigration will slow migration or keep migrants out of the social, economic, and political mainstreams, or conversely, whether migrants and their allies will become strong enough to create political dynamics in their favor. This paper examines those two plausible trajectories. I first review the politically most salient demographic features of mass migration. I then use the conceptual framework of policy feedback – the idea that policies change politics, which in turn reinforce, change, or undermine the initial policy for the analysis-- to consider the conditions in which a country changes in response to the demographic pressures of immigration, and those in which political resistance to further immigration or to immigrants’ incorporation into the receiving country’s mainstream might carry the day. The paper concludes with a brief case study of what happens when the forces of change and inclusion are balanced against those of resistance and exclusion. I focus primarily on the United States, but to some degree refer to other countries as well.