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.

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."

'Something that's leading him'
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.

Charm on full display
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.

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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.

Sen. 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.

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