Until recently, many political scientists had believed that the stability of democracy is assured once certain threshold conditions – prosperity, democratic legitimacy, the development of a robust civil society – were attained. Democracy would then be consolidated, and remain stable. In this article we show that levels of support for democratic governance are not stable over time, even among high-income democracies, and have declined in recent years. In contrast to theories of democratic consolidation, we suggest that just as democracy can come to be “the only game in town” through processes of democratic deepening and the broad-based acceptance of democratic institutions, so too a process of democratic deconsolidation can take place as citizens sour on democratic institutions, become more open to authoritarian alternatives, and vote for anti-system parties. Public opinion measures of democratic deconsolidation are strongly associated with subsequent declines in the actual extent of democratic governance and predict not only recent democratic backsliding in transitional democracies, such as Venezuela or Russia, but also anticipated the downgrades in Freedom House scores occurring across a range of western democracies since 2016.