A special House committee drafted articles of impeachment against Johnson—that is, specific accusations of "high crimes and misdemeanors." Adopted by the House on 2 and 3 March, the articles totaled eleven. The first eight were variations on the charge that Johnson had violated the Tenure Act by attempting to supplant Stanton with Thomas; the ninth and tenth contained petty and patently absurd allegations; and the eleventh, primarily the handiwork of Stevens, combined all of the previous charges. On 4 March seven Republicans, acting as the "impeachment managers," formally presented the articles to the Senate, which sat as a "High Court of Impeachment" presided over by Chief Justice Salmon P. Chase. Two days later, the Senate summoned Johnson to stand trial beginning 13 March.
Johnson reacted to impeachment calmly. "If I cannot be President in fact," he told his personal secretary, "I will not be President in name alone." To defend him, he retained the services of several of the nation's leading lawyers. Pleading the need for more time to prepare their case, they succeeded in getting postponement of the trial. In the meantime, the Republicans passed a bill that deprived the Supreme Court of jurisdiction over cases such as Ex parte Milligan . Thus, Johnson was frustrated not only in his effort to challenge the Tenure Act in the courts but also in his hope of having Military Reconstruction declared unconstitutional.
On 30 March the impeachment trial, which the president was not required to attend in person, got under way. Johnson's attorneys argued that the Tenure of Office Act was unconstitutional; that even if it were constitutional, it did not protect Stanton because he had been appointed by Lincoln, not Johnson; that the president had not actually violated it, since Stanton obviously still remained in office; that Johnson's attempt to replace Stanton was motivated by a legitimate desire to test the act's constitutionality and not by criminal intent; and, finally, that since impeachment was a judicial and not a political process and since Johnson had not committed any indictable offense, the president was innocent of "high crimes and misdemeanors." The House managers, with Benjamin Butler of Massachusetts being the main spokesman, rebutted the defense's allegations about the Tenure Act and maintained that impeachment was political in nature; otherwise, Butler sarcastically asked, how could an unfit president be removed unless he was caught "robbing a chicken house" or committing some other statutory crime?
The managers believed that the catchall eleventh impeachment article offered the best prospect for convicting Johnson. Therefore, on 16 May the Senate voted on it first. Thirty-five senators declared Johnson guilty, and nineteen declared him innocent. Since under the Constitution at least two-thirds of the senators present and voting are needed to convict a president, Johnson escaped by the narrowest possible margin. Ten days later, votes on two other articles provided the same outcome, whereupon the impeachment trial ended.
Johnson owed his escape to the fact that seven Republicans joined with the Senate's ten Democrats and two Conservatives to vote for acquittal. A combination of factors explains why these seven "recusants" deserted their party's ranks: they doubted the legal justification of impeachment, feared that deposing the president would ultimately injure the party, and disliked the prospect of the ultra-Radical Senator Benjamin Wade of Ohio replacing Johnson, which under the presidential succession law of that time he would have done by virtue of being president pro tern of the Senate. Johnson also helped his own cause by letting it be known that if he remained in office, he would cease obstructing the implementation of Military Reconstruction and that he would appoint the politically neutral Major General John M. Schofield to be the new secretary of war—promises he kept. (Stanton resigned as soon as the impeachment trial ended.)
Today practically all historians and legal experts agree that Johnson was innocent of the charges brought against him, and in 1926 the Supreme Court did what Johnson had hoped for in 1868—it declared the Tenure of Office Act unconstitutional. On the other hand, the oft-expressed view that Johnson's removal from office would have permanently weakened the presidency probably is erroneous. The circumstances that led to Johnson's impeachment were both extreme and unique, whereas the forces that brought about the emergence of the "imperial presidency" in the twentieth century would have operated regardless of the outcome of Johnson's trial. Finally, although the impeachment as such failed, it did cause Johnson to abandon his struggle against Congress' Reconstruction program. Despite having declared that he did not want to be president in name alone, in effect he settled for exactly that.