The president asserts influence over Congress by the use of the bully pulpit and the presidential veto. The bully pulpit is a term that refers to the use of the power of a political office to convince people of an idea or piece of legislation. If Congress passes legislation that is undesirable to the president, then the president may issues a veto and return the legislation to Congress.
The three branches of government work independently, and the president has no direct influence over Congressional matters. By the use of the bully pulpit, the president rouses the citizenry to press their Congressional representatives for the outcome the president desires. If a bill passes through the legislature despite the president's use of the bully pulpit, the president has the option to refuse to sign the legislation and send the legislation back to the originating body. Congress then needs a two-thirds majority to override the presidential veto and make the bill into a law without a presidential signature.
The president uses both the bully pulpit and veto option sparingly in order to concentrate presidential power. Presidential threats to veto legislation are more common and offer a warning to Congressional members to prevent a bill from going to the floor of either chamber for a vote.