McDonald specializes in the American electoral system. Leading the United States Elections Project, he calculates turnout rates that are widely used by academics, media, and policymakers. As co-leader of the Public Mapping Project – an effort to increase transparency and public participation in redistricting – he helped develop DistrictBuilder, open-source web-based redistricting software. He has worked to improve election administration through projects with the Federal Voting Assistance Project and the Pew Center for the States, among others. He is a member of the Advisory Board of the Non-Profit Voter Engagement Network, the largest source of nonpartisan resources to help nonprofits integrate voter engagement into their ongoing activities and services.