Democracy and slavery collided in the early American republic, nowhere more so than in the Democratic-Republican party, the political coalition that elected Thomas Jefferson president in 1800 and governed the United States into the 1820s. Joining southern slaveholders and northern advocates of democracy, the coalition facilitated a dramatic expansion of American slavery and generated ideological conflict over slaveholder power in national politics. Slavery was not an exception to the rise of American democracy, Padraig Riley argues, but was instead central to the formation of democratic...