Final answer:
Andrew Johnson alienated both parties due to his lenient Reconstruction policies, opposition to the Fourteenth Amendment and civil rights for freed slaves, and his conflicts with Congress, specifically over the Tenure of Office Act.
Step-by-step explanation:
Andrew Johnson fell out of favor with both Democrats and Republicans for a number of reasons, which can be summed up by his lenient Reconstruction policies and opposition to civil rights, which angered Republicans, and his clash with Congress over the Tenure of Office Act, among other issues. Johnson's willingness to be lenient with the South and to swiftly reincorporate Southern states into the Union, as well as his opposition to the Fourteenth Amendment and civil rights for freed slaves, alienated him from the Radical Republicans. At the same time, his confrontational manner and lack of political finesse led to conflicts with Congress, culminating in his impeachment. These actions and his political stances did not endear him to many Democrats either, who were opposed to his initial punitive stance toward Southern aristocrats.