The Radical Republicans who pushed the harsh Reconstruction measures through Congress after Lincoln's death lost public and moderate Republican support when they went too far by?

The Radical Republicans lost public and moderate Republican support primarily due to their aggressive approach in attempting to impeach President Andrew Johnson. After Lincoln's assassination, Johnson, who succeeded him, adopted a more lenient policy towards the South. The Radical Republicans believed that his policies were obstructing their goals for a robust Reconstruction that would secure rights for freed African Americans and reshape the Southern political landscape. Their push for impeachment was seen as an overreach and contributed to a growing concern about the political climate, alienating moderate supporters who were wary of such extreme measures. This backlash against their tactics demonstrated that their radical approach could backfire, leading to a loss of political capital at a critical time in US history.