Final answer:
Abraham Lincoln vetoed the Wade-Davis Bill due to its unconstitutionality and potential impact on the reconstruction process. The veto was likely influenced by slavery-related issues and personal disagreement with Congress.
Step-by-step explanation:
Abraham Lincoln vetoed the Wade-Davis Bill because he viewed it as unconstitutional and believed it would hinder the reconstruction process. The bill required fifty percent of voters to declare their loyalty before reconstruction could begin and included provisions that Lincoln felt would force states to abolish slavery and limit his options for creating loyal governments. Lincoln's veto was likely influenced by both slavery-related issues and his personal disagreement with Congress.