The president most commonly regarded as the worst in U.S. history is James Buchanan. He is widely criticized for his ineffective leadership during the critical period leading up to the Civil War, where his actions and inactions exacerbated sectional tensions and contributed to the dissolution of the Union

. Other presidents frequently ranked among the worst include Andrew Johnson, who was impeached and criticized for his leniency toward former Confederates and failure to protect newly freed Black Americans; Franklin Pierce, whose support of the Kansas-Nebraska Act intensified pre-Civil War violence; and Herbert Hoover, blamed for inadequate responses to the Great Depression

. More recently, Donald Trump has been ranked among the worst presidents by some historians and surveys, due to his impeachments, legal issues, and controversial actions, including attempts to overturn the 2020 election results

. In summary, James Buchanan is most often considered the worst president historically, with others like Andrew Johnson, Franklin Pierce, Herbert Hoover, and Donald Trump also frequently cited in this context.