The central actors in the party-in-government comprise the president, the the majority and minority leaders in the house and senate, party whips in congress, and state governors.

The correct answer here is the Speaker of the House.

By the Article I, Section 2 of the United States Constitution the office of the Speaker of the United States House of Representatives was established. The Speaker of the House is the correct answer here as he comes from the majority party and he is the party leader in the House of Representatives.