This article explores the national conservatism in the Trump era which led the challenge to the traditional Republican conservatism characterized by threefold ideas of market liberalism, social conservatism, and hawkish internationalism. The national conservatism highlights nation, nation-states, culture, religion, and common good. These concepts have been largely ignored by the classical liberalism that has long sustained the modern American conservatism. This article also explains how the emergence of national conservatism is related to the weakening of the three-legged-stool conservatism of the Republican party by revealing the relatively weak status of market liberalism and international interventionism, and the energized status of social conservatism leaning toward Christian nationalism. Finally, this article introduces the criticism of national conservatism by showing that its interpretation of the American constitutional foundation is tendentious, thereby retreating into authoritarianism.