Which power allows Congress to override a presidential veto?

The ability of Congress to override a presidential veto is established in the U.S. Constitution, specifically in Article I, Section 7. To successfully override a veto, Congress must achieve a two-thirds majority vote in both the House of Representatives and the Senate. This requirement ensures that there is substantial bipartisan support to counter the president's objection to a bill.

A simple majority would not provide enough consensus to demonstrate that the legislative branch collectively disagrees with the president's decision. A unanimous vote is impractical and unlikely in a body as large and diverse as Congress. Similarly, a three-fourths majority is related to constitutional amendments, not to overriding vetoes. Therefore, the two-thirds majority is the correct mechanism that Congress employs to demonstrate its authority over legislation, even in the face of presidential opposition.