On Aug. 28, Barack Obama will deliver one of the most eagerly anticipated speeches in American political history. As the country’s first African-American presidential candidate and possibly the most renowned political orator of his generation, the pressure on Mr. Obama to say something unique and memorable is extraordinary.

But Mr. Obama’s task is far simpler than the drama of the moment might suggest. He must do what every “change” candidate from Franklin D. Roosevelt and John F. Kennedy to Ronald Reagan and Bill Clinton has done: frame the election as a clear choice between change and the status quo.

It is hardly a message that Mr. Obama will be challenged in defining — it has been the essence of his political appeal and electoral success. Like few candidates in American history, Barack Obama, in both his rhetoric and his physical appearance, embodies the notion of political change.

At a time when approximately 80 percent of the electorate believes that the United States is on the wrong track, Mr. Obama is well positioned to take advantage of the country’s sour mood. And here’s how he can do it:

Use Your Political Foil: Just as Franklin D. Roosevelt had Herbert Hoover and the Great Depression; John F. Kennedy had Richard Nixon and the drift of the Dwight D. Eisenhower years; Ronald Reagan had the “malaise” of Jimmy Carter; and Bill Clinton had George H. Bush and the backdrop of an economic recession, Mr. Obama has John McCain and the Bush years.

Mr. Obama could ask for few better political contrasts. Mr. McCain has served in Washington for 26 years, has regularly voted with President Bush (the most consistently unpopular president in American history) and because of his advanced age is the antithesis to the notion of political change that Mr. Obama embodies. Already Mr. Obama and his running mate, Senator Joseph Biden, are regularly linking Mr. McCain to President Bush, and one can expect more of that in Denver this week. Indeed, making the Bush-McCain connection is probably the Democrats’ most effective message and one they seem comfortable delivering.

Don’t Get Caught in the Details: Mr. Obama’s political ascendancy did not come from the fact that he had a better 10-point health care plan than Hillary Clinton; it came from his ability to craft a more compelling political narrative and lay out a vision of America that energized and inspired a majority of the Democratic electorate. The latter has always been a greater harbinger of political success than the former. Most Americans already believe that Democrats are better than Republicans on domestic policy issues; they aren’t necessarily looking for specifics, but instead a clear sense of what an Obama presidency will entail, how he will seek to achieve his ambitious goals and his overall approach to governing.

Avoid Partisanship: Some on the Democratic left have complained that Mr. Obama is not being partisan enough, but divisive partisanship has rarely been an effective political tool for Democrats. For a party that relies on legislative accomplishment and in turn compromise, national consensus should be their key political aspiration. Mr. Obama would be wise to play off the themes of his 2004 keynote speech at the Democratic convention, which sought to bridge the divides between red state and blue state America and sparked his political rise. Today, the desire for an end to political divisiveness is palpable and Mr. Obama’s post-partisan language will stand in sharp contrast to the increasingly negative campaign being waged by his opponent.

The Fear Factor: Mr. Obama must convince skeptical Americans that he can serve as commander in chief and be trusted with the nation’s highest office. Change and relatively unknown candidates -- not to mention ones with Hussein for a middle name -- can seem scary. Therefore, it’s critical for Mr. Obama to orient his message of change in universal and shared American values. Just as Kennedy spoke in the metaphoric imagery of the American frontier and Reagan evoked Franklin Roosevelt and the “greatness” of America’s past, Barack Obama must continue to cast his personal narrative as a quintessentially American story of opportunity and the realization of the American Dream.

Don’t Forget Hope: When Mr. Obama won the Democratic caucus in Iowa last January he spoke words that are among the most powerful he has delivered on the campaign trail:

Years from now, you’ll look back and you’ll say that this was the moment, this was the place where America remembered what it means to hope …. Hope is the bedrock of this nation. The belief that our destiny will not be written for us, but by us, by all those men and women who are not content to settle for the world as it is, who have the courage to remake the world as it should be …. We are not a collection of red states and blue states. We are the United States of America. And in this moment, in this election, we are ready to believe again.

Ultimately, hope of a better future and in particular a better America is one of the most powerful political emotions on the campaign trail. Bill Clinton understood this when he declared “I still believe in a place called Hope”; Reagan understood this when he called for a renewal of “the American spirit and sense of purpose.” For Mr. Obama, “we are ready to believe again” seems a fitting slogan for a campaign focused so heartily on the notion of real political change.