Mr Trump fuelled the flames of those saying her husband was a “secret Muslim” born in Kenya, where his father is from, and not really an American citizen, for several years of his presidency.
“The whole [birther] thing was crazy and mean-spirited, of course, its underlying bigotry and xenophobia hardly concealed. But it was also dangerous, deliberately meant to stir up the wingnuts and kooks,” Ms Obama writes in her forthcoming memoir, Becoming.
Ms Obama has been mum on criticising the president openly, often saying as she did during the 2016 campaign: “When they go low, we go high.”
But, Mr Trump’s continuous attacks on her husband, minorities, immigrants, and other people seem to have pushed the former legal professor.
“What if someone with an unstable mind loaded a gun and drove to Washington? What if that person went looking for our girls? Donald Trump, with his loud and reckless innuendos, was putting my family’s safety at risk. And for this I’d never forgive him,” she adds, in excerpts that have emerged.
The conspiracy theory first surfaced in 2008 but Mr Trump began stirring it up again in 2011 when Mr Obama began running for re-election.
Mr Trump said that year on the Today programme: “I would like to have him show his birth certificate, and can I be honest with you, I hope he can. Because if he can’t, if he can’t, if he wasn’t born in this country, which is a real possibility ... then he has pulled one of the great cons in the history of politics.”
Eventually, towards the end of his run for president in 2016, he admitted he thought Mr Obama was born in the US but never accepted responsibility for his previous actions.
Ms Obama’s book reveals more about her personal life as well, including that she and her husband went through marriage counselling when they needed it and that her daughters, Sasha and Malia, were both conceived through in vitro fertilization.
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