WASHINGTON - The amazement was on their faces. Hundreds waited for Barack Obama on that evening in South Carolina, 15 weeks ago, to claim victory -- a surprising victory, surprisingly large.

And amazing it was. It made it possible for him to stand today on the verge of being the first black person ever nominated for president by a major party.

One could guess the thoughts of the blacks and whites in that crowd: Can you believe that our state -- South Carolina, first to secede and first to open fire in the Civil War -- is now catapulting a black man to the front of the presidential contest in a year that bodes well for Democrats?

"Race doesn't matter,'' some began to chant. "Race doesn't matter!''

The cry soon gave way to more familiar chants of "Yes we can,'' and everyone in the auditorium surely knew that race does still matter in so many ways. But in a pinch-me moment, they seemed to realize that a barrier had been broken with a swiftness and certainty that even they had not foreseen.

Even more astounding, the man vaulting ahead of the universally known Senator Hillary Rodham Clinton, had been a state legislator only four years earlier, a lawyer with no fame, wealth or family connections.

Now, the entire country and countless foreigners are absorbing a moment that had seemed decades away, if possible at all. Smart strategists and rank-and-file voters ponder how Obama rose so far so fast, and theories abound. Historians will sort it out someday, but Obama's blend of oratory, biography, optimism and cool confidence come to mind most immediately.

It's not just about him, of course. If America can seriously think of putting a black man in the White House, surely it must also profoundly rethink the relevance of race, the power of prejudice, the logic of affirmative action and other societal forces that have evolved slowly through the eras of Jim Crow, desegregation and massive immigration.

Maybe the toughest question is this:

Is Obama, with his incandescent smile and silky oratory, a once-in-a-century phenomenon who will blast open doors only to see them quickly close on less extraordinary blacks?

Or is he the lucky and well-timed beneficiary of racial dynamics that have changed faster than most people realized, a trend that presumably will soon yield more black governors, senators, mayors and council members?

Someone special?

Presidential campaigns have destroyed many bright and capable politicians. But there's ample evidence that Obama is something special, a man who makes difficult tasks look easy, who seems to touch millions of diverse people with a message of hope that somehow doesn't sound Pollyannaish.

Representative Elijah Cummings, a black Maryland Democrat who endorsed Obama early, says the Illinois senator convinces people of all races that Americans as a society, and as individuals, can achieve higher goals if they try.

"He says we can do better, and his life is the epitome of doing better,'' says Cummings, noting that Obama was raised by a single mother who sometimes relied on food stamps. "He convinces people that there's a lot of good within them.''

And why should they believe such feel-good platitudes? "Because he's real and he has confidence in his own competence,'' Cummings says.

Without question, Obama is an electrifying speaker. At virtually every key juncture in his trajectory, he has used inspirational oratory to generate excitement, buy time to deal with crises, and force party activists to rethink their assumptions that a black man with an African name cannot seriously vie for the presidency.

A prime-time speech at the Democratic convention in Boston catapulted him to national attention in 2004. When his presidential campaign badly trailed Clinton's high-flying operation, he gave it new life with a timely Iowa speech that outshone her remarks moments earlier on the same stage. And a heavily covered March 18 speech about race relations calmed criticisms about his ties to his former pastor, although Obama had to revisit the matter when the minister restated incendiary remarks about the government.

Obama has a compelling biography, too. The son of a black African father he barely knew, and a white Kansan mother who took him from Hawaii to Indonesia, he was largely raised by his white maternal grandparents. He finished near the top of his Harvard law class, then rejected big firms' salaries to work as a community organizer in Southside Chicago, where he found a church, his wife and a place that felt like home.

But all those attributes don't explain the Obama phenomenon.

Other great orators have fallen short of the presidency, including Daniel Webster and William Jennings Bryan.

Plenty of brilliant people have tried and failed, too. Bill Bradley was a Princeton graduate, basketball star and Rhodes Scholar.

Intriguing biographies aren't enough, either. John Glenn was an astronaut and American hero, but he couldn't get off the presidential launchpad.

Authenticity

Jim Margolis, a veteran campaign strategist now working for Obama, thinks it is his blend of all these traits, wrapped in "authenticity,'' which makes Obama's message of hope and inclusion seem plausible, not pie in the sky.

Margolis interviewed many of Obama's Harvard classmates for TV ads and documentaries. They told him Obama "was wise beyond his years, and never talked down to people,'' Margolis said.

"He has this amazing ability to connect with people and understand their problems,'' he said. "And through it all, there is this optimism.''

For a politician with only four years of experience at the federal level, Obama also has spot-on instincts, associates say, and a steely confidence in his convictions, in good times and bad. His roughest patch came after Clinton revived her campaign with wins in Ohio and Pennsylvania, and a renewed uproar over Obama's former pastor threatened to consume his campaign.

Obama rejected advice to criticize Clinton more fiercely, and went back to his themes of political and racial reconciliation. His solid win in North Carolina and near miss in Indiana confirmed his judgment.

Obama and his small core of longtime advisers also outsmarted the vaunted Clinton team by focusing early on small caucus states, where he racked up important wins. His fundraising has been nothing short of astounding, with millions of dollars pouring in via the Internet from people who never gave a politician a dime.

Obama fans often search for words to express their attraction.

"He just really electrifies you when you are listening to him,'' said Lena Bradley, 78, a beauty salon owner in Washington. "He has something that's leading him.''

As ephemeral as "something that's leading him'' sounds, it's hard to explain in more clinical terms his impact on people. But it's there.

As recently as June 2006, a lone reporter could travel with Obama in cars and small planes as he campaigned for other Democrats in state after state. On one such visit to Massachusetts and New Jersey, his charm was on full display before crowds of various size, age and ethnic makeup. He made teenagers guffaw by saying people pronounced his name "Yo Mama.'' He quoted scripture in a black church, and set every head nodding.

On a plane ride he talked with the reporter for an hour, on the record, with barely a hint of the nervousness or hedging that most politicians understandably display to someone with a pen, pad and tape recorder.

Before an audience of 300 people in East Orange, N.J., Obama spotted local resident and famous singer Dionne Warwick. He smiled impishly and sang, "If you see me walking down the street,'' the opening line of her hit, "Walk on By.'' The crowd roared its approval of his on-key ad lib.

Some veteran politicians also see "something that's leading'' Obama, whether they can explain it or not.

Senator Dick Durbin (D-Ill.), a longtime friend and supporter, said "nothing was ever the same'' after Obama's Boston speech.

Durbin recalls pulling Obama into a vacant meeting room in Chicago's Union League Club, where both had spoken on a Friday afternoon in November 2006. He felt it was time for his young colleague to decide whether to run for the White House.

"There are moments in life when you can pick the time,'' Durbin said he told Obama. "But when it comes to running for president, the time can pick you. You've been picked. This is your moment.''

A short time later, Obama launched his candidacy.