David Garrow interviewed over 1,000 people for his latest biography Rising Star: The Making of Barack Obama and discovered an incredibly disciplined man with a tendency to mythologise his own story.
Garrow says he realised early on that Obama's 1995 memoir Dreams from My Father was a work of historical fiction – "a myth that he constructed to help himself as a political candidate".
In Dreams from My Father, Obama portrays his youthful years as much more 'African-American tough guy' than they actually were, says Garrow.
Obama's twenties in Chicago were his first real exposure to Black America after a "very fortunate upbringing in Hawaii".
"He's going to a very elite prep school, did too much marijuana, did too much cocaine in New York after college. But once he arrives in Chicago as a 25, 26 year old, he really transforms himself into the person who we saw inaugurated as president."
After making the decision to pursue politics at 26, Obama then went to law school to "credential" himself as a future national political candidate, says Garrow.
He became more strategic as he climbed the ranks.
"In Illinois, his number one defining issue was campaign finance reform and getting big money out of politics, but come 2008 when he's the Democratic nominee that goes entirely by the boards and he declines public funding because he realises changing positions will give him a big advantage over the Republicans.".
Dreams from My Father completely omits the two very important romantic relationships Obama had before meeting Michele Robinson, Garrow says.
Barack's first serious girlfriend was Genevieve Cook, the daughter of an Australian diplomat who he had a relationship with in the mid-1980s.
Then in the late '80s, he had a five-year relationship with a half-Dutch half-Japanese graduate student Sheila Miyoshi Jager.
Jager and another woman who Obama was close to in the late '90s have identical recollections of Obama saying that he imagined he could someday be president.
"Barack very explicitly is telling Sheila – with whom he's living at that time, '87, '88 – that this is what he wants to do and that is why he wants to go to law school at Harvard."
Michelle Robinson Obama initially opposed Barack's political career, believing it was a waste of his talents, Garrow says.
Only after the 2004 speech at the Democratic National Conventional did she get on board with his dream.
Garrow – who describes himself as "a progressive Bernie Sanders-style Democratic Socialist" – says a lot of people of his stripe and a lot of people in Black Chicago were very disappointed in the Obama presidency.
"Because he didn't succeed in reaching out to conservative Republicans and because he really avoided any commitment to Black America."
A number of the advisors Obama chose were more partisan than he was himself, which hurt him, but he could have tried much harder to overcome the intense partisanship in US politics, says Garrow.
He describes Obamacare as "a sad and very disappointing compromise".
"Healthcare in the US remains a dire mess and the Obama presidency, unfortunately, didn't really address that."
Obama's drive and ambition is deeply motivated by the life and death of his father Barack Sr – "a serious alcoholic and abuser of women who dies in a drunken car crash' – says Garrow.
"With Barack, there's an emotional need to succeed, to win, to obtain victory.
"He always believes that he's the smartest person in the room. And if you allow yourself to think that you're always smarter than the other folks, I think that leads you to sometimes sit back."
Last year Garrow let Obama read about 95 percent of the manuscript and spent eight hours going over it with him at the Whitehouse.
"There's much in there that he likes, there's also a good amount in it that he very strongly disagrees with because he wants to stick to the mythical version that he told in his memoir."