Associate editor

David Maraniss, an associate editor of The Post, is the author of “First in His Class: A Biography of Bill Clinton” and the forthcoming “Barack Obama: The Story.” This is the second column in an occasional series on the 2012 presidential candidates’ political lives.

They were born on August days 15 years apart, at opposite ends of the baby-boom generation, Bill Clinton in 1946 and Barack Obama in 1961. Both came into the world under circumstances that made it surpassingly unlikely either boy would grow up to be president of the United States. It is hard to imagine two places further from the centers of power than southwestern Arkansas or Hawaii. Neither state had produced a president before. But there was so much more working against them than geography.

William Jefferson Blythe III and Barack Hussein Obama II were the namesakes of fathers they did not know. Billy’s dad, a traveling salesman from Texas, was killed in a car crash before his son was born. Barry’s old man, a traveling student from western Kenya, also died in a car crash. His son was 21 then but had never lived with his father. Both boys’ mothers created myths about their fathers to ease the pain; in truth, the sons were almost certainly better off without them.

There was enough turmoil in the lives of young Billy and Barry without their philandering, unpredictable fathers around. They both had strong, supportive mothers who nonetheless were gone for years at a time, pursuing careers. Billy’s mother, Virginia, went away when he was 3 and 4 so that she could study advanced nursing in Louisiana. Barry’s mother, Stanley Ann, left him behind in Hawaii, starting when he was in fifth grade, so that she could pursue anthropological work in Indonesia. In both cases, the boys stayed with grandparents who were doting but carried their own burdens. Clinton’s mammaw, also a nurse, was addicted to morphine. Obama’s tutu, a bank official, was dependable and pragmatic but a closet alcoholic. Clinton also had to deal with an alcoholic stepfather (from whom he took his last name). Obama had an Indonesian stepfather who was less volatile but no male role model.

Clinton grew up in the segregated South just as it was starting to change, and the idealistic side of his nature was driven by civil rights. In the deepest sense, he knew where he was from. Obama grew up in polyglot Oahu, a hapa — the Hawaiian term for someone of mixed heritage — in a place full of hapas, though most were some variety of Anglo and Asian and very few African American. He was biracial and cross-cultural, and in those senses, unlike Clinton, he was from everywhere and nowhere. In terms of intelligence and ambition, Clinton seemed more the exception in his family; it is hard to trace through his bloodlines where he got his brainpower. In Obama’s lineage, that inheritance is more obvious: Both parents were academic achievers with first-rate minds and graduate educations, though his father, once he had left Harvard and returned to Kenya, called himself “Dr. Obama” despite never having finished his doctoral thesis.

Among the characteristics the young Clinton and Obama shared was competitive will. My favorite story about that trait in Clinton is the time the young son of one of his aides spent a weekend afternoon playing the pinball machine at the Arkansas governor’s mansion and racked up a new high score — an upstart challenge that inspired Clinton to stay up that night, swaying and shaking and tilting the machine, until he had seized back the record from the kid. Anyone who played golf, basketball or poker with Obama saw that same need to prevail, and he could be obnoxious about it. Will Burns, who worked for Obama when he was a state senator, recalls walking the precincts of their district in the fall of 1997, rounding up petition signatures for Obama’s first reelection campaign. “Obama was even competitive about getting signatures,” said Burns, now a Chicago alderman. “We would go to someone’s door and he would say afterwards, ‘See how smooth that was. See how good I am at this. I got a full sheet! You only got a half sheet.’ And I would think, ‘Well, you’re the [expletive] candidate, of course you got a full sheet!’ That was him.”

Clinton came out of his circumstances hot, needy, sprawling. He could not stand to be left alone. So desperate was he for companionship that he was known to invite friends over just to watch him work a crossword puzzle. Obama emerged cool, a lone searcher, self-contained. There is a phrase in native Hawaiian pidgin that captures his demeanor: cool head, main thing.

Clinton’s approach was to forget the past, wake up and forgive himself and the world every day, push past the imbalances in his life and plow forward. Figure out a way to survive and move on. Obama thought that he could not find his future until he resolved his past and made himself whole, piecing together the broken parts. After he turned 18, he essentially devoted the next decade to solving the riddle of his own life. He wrote about his struggle in letters and daily journals, and later poured much of that into a memoir published before he turned 35.

These diametrically different approaches got both men where they wanted to go and then helped define their presidencies. What Clinton had pushed out of the way, unresolved, followed him into the White House. This created trouble, but he was steeled for it by his tactical, just-keep-going adaptability. Obama, on the other hand, had worked so hard to bridge the divides of his life and the contradictions of the world that he came to the job thinking he could accomplish that on a larger scale. If he could get past struggle to resolution, why could the partisans of Washington not do the same? This notion, which some saw as naive, has brought its own set of problems, to which he is now adjusting, but it was above all an expression of self-identity, what he wants to be.