Abstract: Why does science, which is believed by academics and practitioners as enhancing the effectiveness of pandemic governance, fail to perform as well as it should in some cases? The U.S., with its world-leading scientific and technological capabilities and conditions conducive to pandemic governance, provides a case in point for understanding this issue by falling into the dilemma of ineffective governance in the early stages of the pandemic. Scholars' discussions of U.S. pandemic governance from the perspectives of political institutions, political culture, or social inequality cannot adequately explain the paradoxical problem of scientific advantages and governance inefficiency. A comprehensive analysis of its policy contents and implementation in the early stages of U.S. pandemic governance reveals that political overshadowing on science is the important cause of ineffective governance. Existing studies usually discuss the four mechanisms of political intervention in science in the context of the "goal-instrument" relationship, including constraint, intermediate, oversight, and exploitation. Unlike these four mechanisms, The mechanisms of overshadowing is the act of policymakers who put political interests first in scientific issues and repress science through a series of measures, resulting in the alienation of scientific issues into political issues, and can be analyzed from three dimensions of governance goals, expression of opinions, and operational logic. Specifically, in the early governance practices of the U.S. pandemic, repressive measures such as distorting scientific prevention goals with economic performance goals, constraining the expression of scientific opinions with political preferences, and alternating scientific logic with political logic directly led to the dilemma of ineffective governance. So why does politics overshadow science? Established explanations for the causes of intervening mechanisms usually unfold along the lines of political identity pressures or institutional pressures, but fail to adequately respond to the reasons why the overshadowing mechanisms occur. Research has found that the authoritarianization of the Trump administration is the root cause for the occurrence of the overshadowing. Trump's pursuit of power and authority during his presidency has characterized the authoritarianization of the federal government, leading to the political overshadowing on science in the pandemic governance. The political preference for decision-making provides the motivation for the overshadowing mechanisms; the expansion of power by political leaders creates the conditions; and political leaders use the anti-intellectual trend to create the environment. Political overshadowing on science may occur in many areas of modern state governance, and the overshadowing issue still requires further discussion in terms of its extent, types, and motivations.