Question

What did President Johnson do that stunned political backers after he took office?

Answer 1

The answer is Andrew Johnson changed his views on Reconstruction and his policies were more lenient than he had implied he would be.  

Following the assassination of the abolitionist President Abraham Lincoln in 1865, Andrew Johnson, former Vice President, became President. At the moment, politicians who supported Lincoln's government and who knew Andre J. as a backer of the small farmer and knew about his opposition to the slavery and the southern aristocracy, expected that Johnson would act similar to Lincoln when addressing the issues of slavery, inequity to African American and the readmission to the Union of the 11 former Confederate states.

However, Johnson's policies were too far more lenient than expected. He gave no regulation to the Southern states, which later sought to subjugate freed slaves via harsh laws (the Black Codes), he gave no rights to African Americans to participate in any political affair nor receive education or improve their economic status, and he did not condemn any abuse toward black people given by whites Southern (and the abuses were plentiful and frequent). Furthermore, not only did he grant thousands of pardons to white Southerners, wealthy planters and some Confederate leaders but also allowed some of them to return to power or to have their property back.

Answer 2

After taking office, President Johnson completely changed his views on Reconstruction, which stunned political backers. Hope this helped :)