Cross of Gold

 The [Cross of Gold] speech immediately transformed [William Jennings] Bryan from a presumptuous youngster in the rear ranks of the peripheral candidates into a top contender for the nomination. His performance became the standard example of the ability of an orator to sway a convention. In 1953, a poll of 277 professors of American history or government ranked the "Cross of Gold" speech among the fifty most significant documents in American history.

(from A Righteous Cause, by Robert W. Cherny)