Francis Fukuyama in American Purpose:
The “democracy” under attack today is a shorthand for liberal democracy, and what is really under greatest threat is the liberal component of this pair. The democracy part refers to the accountability of those who hold political power through mechanisms like free and fair multiparty elections under universal adult franchise. The liberal part, by contrast, refers primarily to a rule of law that constrains the power of government and requires that even the most powerful actors in the system operate under the same general rules as ordinary citizens. Liberal democracies, in other words, have a constitutional system of checks and balances that limits the power of elected leaders.
Democracy itself is being challenged by authoritarian states like Russia and China that manipulate or dispense with free and fair elections. But the more insidious threat arises from populists within existing liberal democracies who are using the legitimacy they gain through their electoral mandates to challenge or undermine liberal institutions.
More here.