Obama — who's been in the Senate less than three years — faces Clinton and a field of Democrats who have much longer resumes on everything from health care policy to the Middle East. His relative freshness helps him drive home that he is the true change candidate in 2008.
"I have to point out there are a couple of guys named Dick Cheney and Donald Rumsfeld who had two of the longest resumes in Washington, and they led us into the worst foreign policy disaster in a generation," Obama says.
The nation was introduced to Barack Obama when he gave a dynamic speech at the Democratic National Convention in Boston in 2004. He focused on his story — an update of Horatio Alger — recounting the different worlds of his white mother from Kansas and his black father from Kenya. His father, Obama said, had grown up herding goats and going to school in a tin-roof shack.
That speech foreshadowed some of the style and substance voters would be seeing more of: his message of inclusiveness and his self-effacing humor, referring to himself as the "skinny kid with a funny name."
Obama often says his wife, Michelle, a Chicago native and like him a graduate of Harvard Law School, keeps him humble and in check.
Obama's campaign rallies are designed to pump up a rock-star persona, with thumping rock-and-roll and R&B, from Dave Matthews to Gnarls Barkley, aimed at often-youthful crowds. Obama calls out faces in the crowd, laughs at his own jokes and works rope lines with a Bill Clintonesque vigor. Lean and at ease roaming the stage, the 46-year-old's baritone voice invites audiences to participate, and individuals offer shout-outs such as, "We love you, Obama."
Along the way, Obama has picked up many celebrity backers, none more powerful than media mogul Oprah Winfrey. Her recent rallies for Obama in Iowa, New Hampshire and South Carolina drew thousands of people.
Obama's dialect sometimes reflects his audiences. Speaking in Manning, S.C., in November he took on the cadence of a Southern preacher that had not been evident in an intense debate in Philadelphia just a few nights before.
However in debates, he is not as smooth, and it is in these free-for-alls that his lack of experience shows.
Before a debate Oct. 30 in Philadelphia, Obama's campaign aides spent nearly a week saying he needed to get tougher in highlighting his differences with Clinton. But when his time came, the more aggressive John Edwards overshadowed Obama.
Frank Luntz, author of "Words that Work," a book about political communications, says Obama came into the presidential race with the high expectations of his seminal convention speech.
"Expectations were so high when he first came in, he was such a breath of fresh air, and so inspirational," Luntz says. "But the power of his message was not in individual details, it was the global picture, and in these debates he gets into the minutiae, and he thinks too much. You can almost see him go through the thought process: How do I demonstrate how I know what I am taking about; how do I throw in a fact and figure?"
Luntz maintains that Obama has gotten better in debating but has not been able to draw contrasts between himself and Clinton.
Barack Obama's overall theme is inclusiveness, change, and what he calls "the audacity of hope."