Han’s expertise lies in the areas of civic engagement, political organizing, democratic leadership development, and political polarization. Specifically, she studies the way people become motivated to get involved in politics, looking particularly at the organizing practices democratic institutions can use to engage people. She also studies the causes and consequences of polarization in the United States. She has conducted trainings and research with a number of different organizations interested in political organizing, including the Center for Community Change, the New Organizing Institute, MoveOn, Doctors for America, the Sierra Club, the Institutes for Healthcare Improvement, Greenpeace, and others. Han acted as co-convener of a Policy Advisory Committee for the 2008 Obama campaign, Chair of the Advisory Committee to the EAC Agency Review Team on the Obama-Biden Transition Team, and served as National Issues and Policy Advisor to Senator Bill Bradley’s presidential campaign in 1999-2000. From 2008-2011, Han sat on the Sierra Club's Volunteer Leadership Advisory Committee, an advisory committee to the national board.