If the race for the White House were decided on the basis of political oratory alone, then the 2008 campaign would be a hot-air landslide.

Whether they embrace his politics or not, almost everyone – from political junkies to casual observers – agrees that Democratic Sen. Barack Obama of Illinois is the best orator among the current crop of candidates.

“Barack Obama bringeth rapture to his audience,” Jack Shafer, editor of the online magazine Slate, wrote recently. “They swoon and wobble, regardless of race, gender, or political affiliation, although few understand exactly why he has this effect on them.”

Such is the power and skill of a talented orator.

From Winston Churchill (“We shall fight on the beaches …”) to Franklin D. Roosevelt (“The only thing we have to fear is fear itself”) to the Rev. Dr. Martin Luther King Jr. (“I have a dream”), there is a long line of historical figures who have distinguished themselves with their words. The very best project themselves – and their ideas – into posterity.

There’s no clear science about how this happens. Still, academics and social scientists have created a cottage industry out of distilling the essence of successful speechmaking.

Martin J. Medhurst, a professor of rhetoric and communications at Baylor University in Waco, Texas, is editing a book on the topic.

“Words of a Century: Top 100 American Speeches, 1900-1999” is to be published later this year by Oxford University Press. It’s heavy on memorable public addresses by social activists and political leaders.

The list ranks King’s “I have a dream” speech as the best of the century, followed by President John F. Kennedy’s inaugural address and Roosevelt’s first inaugural address. The late Rep. Barbara Jordan of Texas, who placed fifth on the list, is the highest-ranked woman for her keynote address at the 1976 Democratic National Convention.

“The greatest speeches occur at moments of crisis in American history such as during wars, civil rights, women’s suffrage and the like,” Medhurst said. “There’s something about a national crisis that calls forth presidential oratory because the president is the one to speak for the nation.”

But it also includes iconic public statements from religious leaders (Jesse Jackson and Elie Wiesel), lawyers (Clarence Darrow), military leaders (Gen. Douglas MacArthur), and one rare and memorable speech by an athlete (Lou Gehrig).

Medhurst praised Obama for his natural and conversational speaking style, elevating him “head and shoulders above” his White House opponents. “He has the ability to be inclusive in his rhetoric, which resonates because it’s so unusual,” he said. “We haven’t heard a politician speak like that in a long, long time.”

As for Obama’s rivals, Democratic Sen. Hillary Clinton of New York and Republicans Sen. John McCain of Arizona and former Arkansas Gov. Mike Huckabee, Medhurst described their political speaking skills as “sort of run of the mill…not appreciatively better or worse than others in the past.”

Paul Martin, a political scientist at the University of Virginia’s Miller Center of Public Affairs, believes the value of a great speaker often lies in the ears of the beholder. A great speaker is one who says what his or her audience wants to hear.

“There’s some psychological research on persuasion that suggests two critical factors: a perception that the speaker is knowledgeable and a belief that you are already on the same side,” he said. “If you think someone disagrees with you, you are very unlikely to accept their arguments.”

Sometimes a great speech pushes a neglected issue into the national consciousness. Activist Mary Fisher focused national attention on AIDS with her speech at the 1992 Republican National Convention.

There are tricks to the trade, said Patricia A. Sullivan, chair of the communications and media department at State University of New York at New Paltz. She said great speakers listen to and mimic outstanding orators to pick up vocal cues and techniques, then practice them until it sounds conversational.

Comparing Obama to abolitionist Frederick Douglass, Jesse Jackson and King, she noted how he employs rhythmic repetition, call-and-response formulas and a conversational tone to bond with those listening to him.

“Obama uses a lot of strategies that are typical of African-American discourse,” Sullivan said. “If you’re going to be that kind of inspirational speaker, it has to come from inside you and it has to be a part of your ethos.”

In particular, she noted Obama’s keynote address at the 2004 Democratic National Convention, a speech that made him a star. Obama tested the themes that have become the staples of his current stump speeches.

“Do we participate in a politics of cynicism or do we participate in a politics of hope?” Obama said to thunderous cheers in that speech. “Hope! Hope in the face of difficulty. Hope in the face of uncertainty. The audacity of hope!”

Sullivan called that speech technically sound, yet inspirational.

“There’s a whole rhythm to the speech,” she said. “The message isn’t just being created by the speaker, but it’s being created by the speaker and the audience, making it a powerful shared experience.”

Most recent presidential candidates have come to public attention as a result of a single speech or series of public orations, said Stephen Lucas, a professor of communications at the University of Wisconsin in Madison.

Ronald Reagan’s “A Time for Choosing” speech at the 1964 Republican National Convention set the stage for his election 16 years later, Lucas said.

Similarly, failed Democratic presidential candidate John Kerry first drew notice in 1971 when he spoke out against the Vietnam War before the Senate Foreign Relations Committee.

“The power of the spoken word has been what has moved large masses of people throughout history,” Lucas said. “Anyone who runs for president nowadays has to perform in public, be on camera all the time. Their speeches say something about who they are and how they will serve, if elected.”

Or not.

Sullivan at SUNY said that even though President George W. Bush was tongue-tied, he won because voters were wary of slick-sounding politicians.

“At that time, people had enough of President Clinton and wanted someone who came across as likable, someone who came into their living rooms over the television and seemed comfortable. It didn’t matter that he didn’t speak very well.”

Sam Fulwood III is a reporter for The Plain Dealer of Cleveland. He can be contacted at sfulwood@plaind.com.