Why do countries’ political regimes change over time—from dictatorship to democracy and vice versa? Competing literatures contend that the key long-run driver is, respectively, economic development or institutional evolution. Other accounts focus on short-run microinteractions among societal actors. I discuss the strengths and limitations of these approaches and suggest ways in which they might usefully be combined. While simple modernization theory implies more cross-national convergence than we have seen, institutional path-dependence predicts too much divergence. Analyses of microinteractions overemphasize deliberate choice and ignore copious historical evidence of confusion and error. They also fail to explain the spread of elections. New approaches posit that microinteractions trigger change while its direction is set by slow-moving structural factors (“conditional modernization theory”) or that economic development has effects at both country and global levels (“global modernization theory”). Other insights may come from disaggregating democracy into subelements, each with a distinct history and logic.