Final answer:
President Lincoln's Ten Percent Plan aimed to rapidly reincorporate the former Confederate states back into the Union by requiring a small fraction of the voting population to pledge allegiance to the U.S. and accept abolition. Congress, especially Radical Republicans, believed the plan to be too lenient.
Step-by-step explanation:
The goal of President Lincoln’s plan for Reconstruction, known as the Ten Percent Plan, was to reincorporate the former Confederate states into the Union as quickly as possible. The plan entailed a lenient approach, offering a general pardon to Southerners, with the exception of high-ranking Confederate leaders, and required only that 10 percent of the 1860 voting population in these states take an oath of allegiance to the United States and assent to the emancipation of slaves. Lincoln also believed that the states should themselves determine how to end slavery, which led to Radical Republicans considering the plan too lenient for not guaranteeing civil rights to formerly enslaved individuals.
Congress, especially the Radical Republicans, challenged Lincoln's moderate approach, preferring that Reconstruction do more than just end slavery, and wanting to implement policies that would ensure civil rights to all citizens. The Wade-Davis Bill, which proposed more stringent requirements for Southern states' readmission, was vetoed by Lincoln, highlighting the tension between his executive approach to Reconstruction and Congress's desire for more control and stricter terms for the readmission of the Southern states.