In the instance when the Presidency and both Houses of Congress are controlled by one party, the Speaker normally assumes a lower profile and defers to the President. For that situation the House Minority Leader can play the role of a de facto "leader of the opposition", often more so than the Senate Minority Leader, due to the more partisan nature of the House and the greater role of leadership. Minority Leaders who have played prominent roles in opposing the incumbent President have included Gerald Ford, Richard Gephardt, Nancy Pelosi, and John Boehner.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What office did Nancy Pelosi at one time consider running for?
unanswerable