The article analyses modern populism as a challenge to liberal democracy in terms of the activities of right-wing and left-wing political parties. An important factor in the growth of populism is the lack of effectiveness of constitutionalism and other formal limited institutions, procedures to ensure the principles of people’s sovereignty, democracy, justice, guarantee the interests of the majority in the modern world. It is noted that populism emerged in the late 19th century as a social movement, ideology, and political activity, and since then has firmly taken its place in the political consciousness of the masses, gaining new features and intensifying at times when countries are experiencing turning points in their history. The main factors in the growth of populism include the insufficient effectiveness of the institutions of indirect democracy in modern consolidated democracies. Another reason for the rise of populism is related to the tendency of ideological deradicalization, which manifested itself in the activities of different parties. Today, populism does not have a developed fundamental theoretical background and conceptual texts like nationalism and conservatism. However, it has a holistic structure as a political phenomenon and a set of ideological positions. The goal of modern populism is the introduction of “illiberal democracy” – a government that ensures smooth transformation of people’s preferences into public policy (unlike liberal democracies, which are almost always hindered by certain obstacles to responding effectively to pressing problems). From this point of view, populism is not a threat to democracy as such, but the leading liberal version of democracy. The possibilities of constitutionalism are treated with scepticism in the populist ideology, as formal, limited institutions and procedures prevent the majority from executing their will. Liberal democracy is not strong enough and constantly needs strengthening elements in response to new challenges and threats. But liberal democracy, more than any other political form, contains the potential for development, a synergistic resource, and the power of self-correction. A strong parliament and a developed civil society remain effective counterweight to populism.