The impeachment and trial of President Andrew Johnson transpired in the shadow of the Civil War and the assassination of President Abraham Lincoln.1 President Johnson was a Democrat and former slave owner who was the only southern Senator to remain in his seat when the South seceded from the Union.2 President Lincoln, a Republican, appointed Johnson military governor of Tennessee in 1862,3 and Johnson was later selected as Lincoln's second-term running mate on a “Union” ticket.4 Given these unique circumstances, President Johnson lacked both a party and geographic power base when in office, which likely isolated him when he assumed the presidency following the assassination of President Lincoln.5
The majority Republican Congress and President Johnson clashed over, among other things, Reconstruction policies implemented in the former slave states and control over officials in the executive branch.6 President Johnson vetoed 21 bills while in office, compared to 36 vetoes by all prior Presidents. Congress overrode 15 of Johnson's vetoes, compared to just 6 with prior Presidents.7 On March 2, 1867, Congress reauthorized, over President Johnson's veto, the Tenure of Office Act, extending its protections for all officeholders.8 In essence, the Act provided that all federal officeholders subject to Senate confirmation could not be removed by the President except with Senate approval,9 although the reach of this requirement to officials appointed by a prior administration was unclear.10 Congressional Republicans apparently anticipated the possible impeachment of President Johnson when drafting the legislation; Republicans already knew of President Johnson's plans to fire Secretary of War Edwin Stanton and the Act provided that a violation of its terms constituted a “high misdemeanor.” 11
