Final answer:
Dennis Hastert, Champ Clark, and Tip O'Neill all served as the Speaker of the House, the highest leadership post in the U.S. House of Representatives and second in the presidential line of succession.
Step-by-step explanation:
Dennis Hastert, Champ Clark, and Tip O'Neill all held the leadership position of Speaker of the House. This role is the presiding officer of the House of Representatives and is considered the most important leadership position within the House. The Speaker is not only the administrative head but also the partisan leader of the majority party in the House and is elected by the entire body of representatives. They also stand second in the presidential line of succession, after the vice president. Below the Speaker are the majority and minority leaders, who are elected by their respective party conferences or caucuses and hold significant power in shaping legislative priorities and party strategy.