David Callahan, founder and editor of Inside Philanthropy, knows a thing or two about giving. And in his recent advice to the country's top donors, Callahan encouraged donations to Heartland Fund's Rural Democracy program.

"It’s not hard to figure out how to give for civic engagement and voter mobilization," he writes. "Just ask other funders who are already working to scale up the most effective organizing groups. You can donate to leading state and local groups directly, and make large gifts to national intermediaries that fund their work, like the Center for Popular Democracy, Movement Voter Project, Way to Win, Rural Democracy Initiative, and the State Infrastructure Fund (which you’ve supported already)."