Richard Neustadt was one of the biggest names in the field of political science in the United States. Specifically, he was one of the most important scholars of the presidency in the late 20th century.
Neustadt is best known for his argument about the power of the presidency. Neustadt claimed that the power of the president was the power to persuade. Neustadt emphasized that presidents in the US political system do not have the power to simply give orders and have Congress do their bidding. This is true even when Congress is of the same party as the president. Instead, the president's real power comes from the fact that he (and someday she) is the person with the highest profile in the political system. His speeches and his press conferences are widely covered by the media. The president is, therefore, given the chance to persuade the people to go along with his ideas.
Neustadt's insight went against the previous view of the "imperial presidency" in which the president's power was seen as much more expansive. It is for this idea that Neustadt was one of the most important American political scientists of the late 20th century.