The previous answer was very strong. I would like to pivot a bit in discussing the contextual significance of the speech. At the point in which the then- Senator Obama delivered the speech, he was far from the established leader that has emerged over the last six years. In February of 2008, the primary process had pit Obama against then- Senator Hillary Clinton for the Democratic Presidential nomination. Clinton was the "establishment candidate," one whose name value was synonymous with expertise, solutions, and practical results. Obama was the transformative figure who captured zealous support with his rhetorical capacity to inspire. As Candidate Obama's support was increasing and posing a serious threat to Candidate Clinton's almost perceived ascension to the nomination, the criticism was offered that Obama was incapable of fundamental leadership. The day before Obama delivered his speech, Clinton argued that "It will take more than just speeches to fulfill our dreams. It will take a lot of hard work." The statement was a direct jab at Senator Obama, and sought to cast him as too idealistic and not to be taken seriously as a candidate for President.
Senator Obama's remarks are effective because he directly challenged such an idea. Senator Obama rhetorically cast the idea that "words" and "dreams" are critical to the very definition of America. When Senator Obama quotes "We hold these truths to be self- evident" and "I have a dream," he is able to link his own candidacy to such transformative moments in American History. The refrain of "Just words?" was effective because it posed a compelling argument that the Clinton campaign simply could not generate an effective counter- response. Words and dreams are the fundamental building blocks to American identity. America was forged as a result of "just words." The American construction of self exists as transformative dreams, to enable to instigate individual imagination that is able to change what is into what can be. The Senator direct accepted the criticism that the Clinton campaign offered and flipped it in suggesting that its aspirations are on the same level as Jefferson, Dr. King, and FDR. The Clinton campaign never intended to place Barack Obama amongst such giants in American History. Yet, the Senator and his staff were smart enough to seize an opportunity, not by running away from something, but rather running towards it.
Senator Obama's speech was effective because it helped to cast the debate between both candidates in a very compelling paradigm. After the speech, it became clear that voting for Obama meant voting for the transformative type of leadership that was evident in Jefferson, Dr. King, and FDr. At the same time, it became clear that Senator Clinton was never going to be the transformative and inspirational figure that was reflective of the time. Senator Obama's speech was a "game- changer" because it put Senator Clinton on the defensive. From that point on, she was never able to assert a narrative in which she was fully in control. She was responsive and reactive, something that could have plagued Senator Obama. Yet, his artful handling of the issue was critically differentiating at a point in the Primary election where neither candidate was effectively able to neutralize the threat of the other. It is in this light where the speech was effective because it helped to create a differentiation between two compelling candidates, making the speech everything that it needed to be.