We study a model of the rise and fall of illiberal democracies. Voters value both liberty and economic security. In times of crisis, voters may prefer to elect an illiberal government that, by violating constitutional constraints, offers greater economic security but less liberty. However, violating these constraints allows the government to manipulate information, in turn reducing electoral accountability. We show how elements of liberal constitutions induce voters to elect illiberal governments that remain in power for inefficiently long---including forever. We derive insights into what makes constitutions stable against the rise of illiberal governments. We extend the model to allow for illiberal governments to overcome checks and balances and become autocracies. We show that stronger checks and balances are a double-edged sword: they slow down autocratization but may make it more likely. We discuss the empirical relevance of our theoretical framework and its connection to real world examples.