This is a little bit complicated but you could say that as Neustadt identified - "the president's power is the power to persuade". Consequently, the president must gain the support and cooperation of the other branches of federal government in order to achieve his policy aims, such as passing legislation that was in his State of the Union Address. The president might offer to help a member of Congress with ensuring the passage of a piece of legislation that benefits that member's state or district. In this way, a pressure group might then lobby this member of Congress to ask the president to support a piece of legislation they desire.
For example, the Chairman of the Senate Standing Committee for Health, Thomas Harkin (Iowa), might be lobbied by the sectional-group the American Medical Association to make an amendment to Obama's healthcare reform bill which Harkin might then propose to Obama which Obama might agree to in return for the committee approving the bill.