Barack Obama and John McCain don’t agree about much, but when, in the middle of one of their debates this month, Obama referred to “those of us, like myself and Senator McCain, who don’t need help [financially]”, his opponent nodded. Whoever comes out ahead in 10 days time, the next president of the United States will be a rich man. McCain made his first million the old-fashioned way: he married the daughter of a wealthy businessman. But Barack Obama, the son of an absent African father and a mother who relied on government-issued food stamps to feed her children, became a millionaire in a more modern manner – on the back of a book deal.

It happened circuitously. In 1990, Obama was already enough of a celebrity – the first black president of the prestigious Harvard Law Review – for the New York publishers Simon & Schuster to offer a “six-figure contract” for a proposed autobiography. The only problem was that Obama was too busy finishing law school to write the book, and the contract was eventually cancelled. By the time Obama finished Dreams From My Father – published by Times Books in 1995 – his advance was only $40,000. In 2004, Obama – now a state senator in Illinois and a candidate for the US senate – was chosen to be the keynote speaker at the Democratic National Convention, but his book was long out of print. Yet when he arrived in Washington, the $169,300 senator’s salary was not going to be his mainstay: two weeks before he was sworn in, Crown Books announced a $1.9m three-book contract with the senator-elect.