Let's reflect on the 50th anniversary of one of U.S. history's virtuoso bully pulpit performances – not one but two speeches, delivered on consecutive days in June 1963. They are a matched rhetorical pair of landmark addresses, one focused on peace abroad and the other on justice at home.

On June 10, 1963 President John F. Kennedy told the graduating class at American University that he had "chosen this time and this place to discuss … the most important topic on earth: world peace." He spoke as a leader empowered by his deft handling of the Cuban missile crisis but also as one more keenly aware than ever of how precarious the Cold War made human existence. He was not, he said, seeking a "Pax Americana enforced on the world by American weapons of war" nor "the peace of the grave or the security of the slave" but "genuine peace ... not merely peace for Americans but peace for all men and women – not merely peace in our time but peace for all time."

Achieving that, he argued, required not only persuading the Soviets that peaceful coexistence was possible, but Americans as well. He warned against seeing "only a distorted and desperate view of the other side," and said that Americans should not view "conflict as inevitable, accommodation as impossible and communication as nothing more than an exchange of threats."

There was an achievable balance, JFK argued, between acknowledging disagreements and letting them define relations. "If we cannot end now our differences, at least we can help make the world safe for diversity," he said. "For, in the final analysis, our most basic common link is that we all inhabit this small planet. We all breathe the same air. We all cherish our children's future. And we are all mortal."

The idea of peaceful coexistence was a radical one in those fraught days at the height of the Cold War, so much so, as I recount in "White House Ghosts: Presidents and Their Speechwriters," that Kennedy and speechwriter Ted Sorensen had bypassed the bureaucracy in the speech's composition, keeping its contents a secret from the State Department and the Pentagon until virtually the last minute.

The speech led to an atmospheric nuclear test ban treaty. And it remains one of the most eloquent presidential statements of war and, as former U.S. diplomat Nicholas Burns argues, "the most important speech by an American president in the last half century."

Even as Kennedy was addressing world peace, domestic matters riveted the country. Two African-American students were scheduled to enroll the next day in the University of Alabama, but Gov. George Wallace had vowed to block them, going so far as to theatrically stand in the door of the registration building.

Civil rights had been a disappointment for Kennedy's liberal supporters who had expected more direct leadership from the Oval Office. "In not doing so, he is acting much as Eisenhower used to act when we denounced him so," Kennedy aide Arthur Schlesinger, Jr., my father, recorded in his diary. For his part JFK was deeply skeptical of the power of exhortation. While people expected him "to go on the air all the time educating the nation," he said, "the nation will listen only if it is a moment of great urgency."

Even with the Alabama crisis peacefully resolved, Kennedy decided that he finally had the nation's ear. "We are confronted primarily with a moral issue," he told the country on June 11. "It is as old as the Scriptures and is as clear as the American Constitution." The issue was not sectional but one facing the entire country, he argued. "A great change is at hand, and our task, our obligation, is to make that revolution, that change, peaceful and constructive for all," he said. In an ad-libbed conclusion he said that, "this is one country. It has become one country because all of us and all the people who came here had an equal chance to develop their talents. We cannot say to 10 percent of the population that you can't have that right."

It was the first time a president had argued that all Americans should have equal access to public accommodations. "He did have to be dragged kicking and screaming to putting civil rights before the Congress but it was a courageous thing to do because he and Bobby [Kennedy] thought it would jeopardize his re-election," historian and Kennedy biographer Robert Dallek says.

Of course, the bill he did introduce stalled, only passing when Lyndon Johnson framed it as a tribute to a fallen president's legacy. Kennedy knew he wasn't going to get the law in his first term, but he charted a course with the speech for his agenda and for the country.

There are lessons in these speeches about the bully pulpit. It's a strategic tool for shaping the national debate; but, as Kennedy understood, the atmosphere surrounding the speech has to be properly aligned: The country must be paying attention. And even speeches history considers great don't necessarily have huge initial impacts: The White House received 50,000 letters in the week after the AU speech, but only 900 touched on his peace address. ("That is why I tell people in Congress they're crazy if they take their mail seriously," JFK remarked.)

Working at such a strategic level can limit the bully pulpit's tactical utility, despite the myth that it can move the public in the immediate term. In the end, the bully pulpit's use might have more to do with posterity than day-to-day politics – especially in the 21st century's fractured media environment. "What is Kennedy remembered for?" Dallek says. "The guy has this tremendous hold on the public imagination, it's because of his rhetoric and because of the hope. … This is what really counts with people. They remember the rhetoric."

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