Refugees, displaced persons, and economic migrants are a growing proportion of the populations of developed countries. In each host country, diaspora communities form around home-country origins. Considerable research has been devoted to these diaspora communities in relation to their adjustment to the host country, whether they are assimilated, integrated, isolated, or marginalized. Relatively rare is research aimed at understanding the impact of diasporas on home-country politics. Sometimes the impact is positive, as when the money and votes of Mexican workers in the U.S. elected Vicente Fox. Sometimes the impact is more negative, as when Tamils in Canada support the Tamil Tiger insurgency in Sri Lanka or Irish Americans support the Republicans in Northern Ireland. Researchers at the Asch Center are currently using polling data from European, Canadian, and U.S. Muslims to find predictors of sympathy and support for jihadist violence, and to distinguish activism (legal and non-violent political action) from radicalism (illegal and violent political action). The concepts and measures being developed can be extended to tracking the political sympathies and activities of diasporas in many countries.