"O'Neill takes on a fundamental puzzles in comparative politics -- Why would national-level politicians decentralize power to subnational governments? She finds theories based on economic efficiency and crisis, external pressure from international actors, and internal ethnic heterogeneity lacking, proposes an alternative, electoral theory of decentralization, and tests it against five cases from the Andean region. The research strategy is elegant and clearly stated, and the results are impressive. This is a terrific contribution to our understanding of decentralization." John Carey, Dartmouth College