Final answer:
Radical Republicans were supported by those who desired drastic reforms and civil rights for African Americans post-Civil War, but hated by proponents of a lenient approach and moderate Republicans. Charles Sumner and Thaddeus Stevens were prominent Radicals, while the party evolution forced some moderates to switch affiliation.
Step-by-step explanation:
The Radical Republicans were appreciated and supported by those who favored a strict approach to Reconstruction and wanted to ensure civil rights for African Americans, as well as drastically reform the Southern states after the Civil War. Individuals such as Massachusetts senator Charles Sumner and Pennsylvania representative Thaddeus Stevens advocated for major changes including integrating schools, giving Black men the right to vote, and redistributing plantation lands.
On the other hand, they were hated by those who supported President Andrew Johnson's more lenient approach towards the South, as well as the moderate Republicans and Democrats who sought reconciliation without the severe punishments and transformations envisioned by the Radicals.
As the party evolved, Moderate Republicans worked with Democrats to achieve social reform. However, as the Republican Party shifted towards a small government and states' rights stance, moderates like Senator Arlen Specter found it difficult to remain, with some eventually switching parties. The Radicals' vision conflicted with proponents of a more lenient approach to Reconstruction and those who wanted a quick reunification of the country, without the extensive changes proposed by the Radicals.