Radicalism did not begin in the Administration of Andrew Johnson. Lincoln had felt its covert opposition throughout the war, but he possessed the faculty of weakening his opponents, while Johnson's conduct usually multiplied the number and the strength of his enemies. At first the radicals criticized Lincoln's policy in regard to slavery, and after the Emancipation Proclamation they shifted their attack to his "ten percent" plan for organizing the state governments as outlined in the Proclamation of December 1863. Lincoln's course was distasteful to them because he did not admit the right of Congress to dictate terms, because of his liberal attitude towards former Confederates, and because he was conservative on the Negro question. A schism among the Republican supporters of the war was with difficulty averted in 1864, when Fremont threatened to lead the radicals in opposition to the "Union" party of the President and his conservative policy.

The breach was widened by the refusal of Congress to admit representatives from Arkansas and Louisiana in 1864 and to count the electoral vote of Louisiana and Tennessee in 1865. The passage of the Wade-Davis reconstruction bill in July 1864, and the protests of its authors after Lincoln's pocket veto called attention to the growing opposition. Severe criticism caused Lincoln to withdraw the propositions which he had made in April 1865, with regard to the restoration of Virginia. In his last public speech, he referred with regret to the growing spirit of vindictiveness toward the South. Much of the opposition to Lincoln's Southern policy was based not on radicalism, that is, not on any desire for a revolutionary change in the South, but upon a belief that Congress and not the executive should be entrusted with the work of reorganizing the Union. Many congressional leaders were willing to have Congress itself carry through the very policies which Lincoln had advocated, and a majority of the Northern people would have endorsed them without much caring who was to execute them.