For the most part, historians view Andrew Johnson as the worst possible person to have served as President at the end of the American Civil War. Because of his gross incompetence in federal office and his incredible miscalculation of the extent of public support for his policies, Johnson is judged as a great failure in making a satisfying and just peace. He is viewed to have been a rigid, dictatorial racist who was unable to compromise or to accept a political reality at odds with his own ideas. Instead of forging a compromise between Radical Republicans and moderates, his actions united the opposition against him. His bullheaded opposition to the Freedmen's Bureau Bill, the Civil Rights Act of 1866, and the Fourteenth Amendment eliminated all hope of using presidential authority to effect further compromises favorable to his position. In the end, Johnson did more to extend the period of national strife than he did to heal the wounds of war.

Most importantly, Johnson's strong commitment to obstructing political and civil rights for blacks is principally responsible for the failure of Reconstruction to solve the race problem in the South and perhaps in America as well. Johnson's decision to support the return of the prewar social and economic system—except for slavery—cut short any hope of a redistribution of land to the freed people or a more far-reaching reform program in the South.

Historians naturally wonder what might have happened had Lincoln, a genius at political compromise and perhaps the most effective leader to ever serve as President, lived. Would African Americans have obtained more effective guarantees of their civil rights? Would Lincoln have better completed what one historian calls the "unfinished revolution" in racial justice and equality begun by the Civil War? Almost all historians believe that the outcome would have been far different under Lincoln's leadership.

Among historians, supporters of Johnson are few in recent years. However, from the 1870s to around the time of World War II, Johnson enjoyed high regard as a strong-willed President who took the courageous high ground in challenging Congress's unconstitutional usurpation of presidential authority. In this view, much out of vogue today, Johnson is seen to have been motivated by a strict constructionist interpretation of the Constitution and by a firm belief in the separation of powers. This perspective reflected a generation of historians who were critical of Republican policy and skeptical of the viability of racial equality as a national policy. Even here, however, apologists for Johnson acknowledge his inability to effectively deal with congressional challenges due to his personal limitations as a leader.