Lincoln, compared to the Radical Republicans of his party, was planning on being far kinder than they wanted him to be. He was planning on letting states back into the Union if a low percentage, 10% I believe, of their population took an oath of loyalty to the Union. His assassination, however, did not bring a harsher President into office. Lincoln's vice president was Andrew Johnson, the only southern senator to refuse to leave his seat in the Union. Johnson was a Southern Democrat and as such he was just as lenient as Lincoln and had a soft heart for the South. As long as you weren't rich and said an oath of loyalty you could join the Union again. If you were rich, aka plantation owner, you had to beg. He didn't make any rules about former office holders so many of the southern leaders of the Confederacy were reelected back to office. He also let southern states simply replace 'slave codes' with 'black codes' which were basically the same thing. So, Lincoln's assassination allowed an even more lenient President into office who's reconstruction plan was very generous to the South and can be seen as allowing for the creation of organizations like the KKK and policies like black codes and Jim Crow laws. That's not to say these wouldn't have popped up if Lincoln had carried out reconstruction but Johnson definitely didn't help keep them down.