The challenge right-wing populism poses to conservatism and liberal democracy in the United States deserves the most accurate of analyses, especially through the prism of an ideological approach. The author investigates ideological structures of American conservatism and populism using Michael Frieden’s method of “ideological morphology”. The methodology of the paper divides ideologies into a thin-centered ideology and a host ideology. The former cateogry, which includes populism, shapes their discourse using the concepts of more universal host ideologies such as conservatism. The ideological contents of American conservatism in most areas (traditionalism, libertarianism, social conservatism, neoconservatism, paleoconservatism) and various types of populism are under examination in the research. The development of the intellectual conservative movement in the United States in correlation with the ideological evolution of populism is investigated. The interrelatedness of American conservatism and populism at different historical stages is revealed. The author defines the basic elements of Trumpism, such as the contrast between ‘pure Americans’ and the ‘corrupt elite’ and the concept of the ‘common people’s will, and considers the role of American conservatism in the formation of Trumpism as a contemporary type of populism in the United States, although, due to the 2020 elections, it is at least temporarily exiting the political scene. Trumpism, on the one hand, creates a threat to liberal democracy in the United States, and, on the other hand, it is not devoid of the potential to correct it. The author has discovered that Trumpism accepts the paleoconservative ideas of foreign policy isolationism and economic protectionism, and has also identified the correlation between Trumpism and traditionalism in the domestic political agenda that existed during the presidency of Donald Trump. The 2020 presidential election results are analyzed in the article in the context of the ideological and political evolution of the Republican Party.