>> that's pretty amazing, the convergence of a media phenomenon and a mature movement coming together to shape politics. >> reporter: like birmingham before it, the brutality at selma shocked the nation, compelling washington to respond -- >> ladies and gentlemen, the president of the united states. >> reporter: this time with the voting rights act of 1965. >> what happens in selma or in cincinnati is a matter of legitimate concern to every american. this is one nation. >> reporter: on march 7th, 2015, america's first black president, barack obama, with john lewis at his side, visited selma to commemorate bloody sunday. >> in one afternoon 50 years ago, so much of our turbulent history, the stain of slavery, and anguish of civil war, the