The significance of the Ten-Percent Plan, introduced by President Lincoln during the Civil War, lay in its approach to Reconstruction. The plan proposed that a Southern state could rejoin the Union once 10% of its voters swore an oath of allegiance to the Union. It aimed to provide a relatively lenient path for the South's reintegration and encourage loyalty among citizens. However, the plan faced criticism for being too lenient and was ultimately replaced by the stricter Radical Reconstruction, highlighting the tensions regarding how to address the post-war South's reintegration.