Final answer:
The threat of a veto provides the president with significant leverage in Congress, as it can lead to legislative changes favorable to the president's position and can influence the crafting of bills before they reach the president's desk.
Step-by-step explanation:
Much of the time, the threat of a veto provides the president with significant leverage in Congress. When Congress sends a bill to the president, the president can return it with objections, using the veto. This act raises the bar, as Congress can only override the veto with two-thirds majorities in each chamber. The mere threat of a veto can be enough to get Congress to enact legislation that aligns more closely with the president's preferences, or to make them consider revisions or compromises. The veto serves as a powerful tool in the president's arsenal, not only to block undesirable legislation but also to influence the shape of laws as they are being drafted.
Veto threats, however, can come with risks. They may backfire, causing political damage or reinforcing negative public perceptions, especially if the president's opposition to certain bills is highly visible. On the other hand, astute use of veto threats can result in legislation changing in the president's favor, as was the case with President Bill Clinton and the welfare reform bill.
Ultimately, the threat of a presidential veto acts as a bargaining chip, granting the president a negotiation tool that is part of the broader power to persuade and a means of achieving policy objectives when working with Congress.