According to a new biography of Barack Obama, the future president once proposed to his white live-in girlfriend, but broke off their relationship when he decided her race would hamper his political career.

In his autobiographies, Obama only alludes to his previous relationships before meeting his eventual wife Michelle, and at times even used a "composite girlfriend." But Pulitzer Prize-winning historian David Garrow managed to track down one of his exes for his new book, Rising Star: The Making of Barack Obama.

Sheila Miyoshi Jager, now an Oberlin professor, was Obama's live-in girlfriend in his early Chicago years before he met Michelle. Jager told Garrow that Obama asked her to marry him twice, once at her parents' house in 1986 and a year later before he went to Harvard Law School. Both times she refused him.

But eventually Obama began to see Jager as a potential liability to his political career in Chicago, where African-American politicians were often looked down upon for marrying outside the race. Illinois state senator Richard H. Newhouse Jr., the Washington Post notes in its review of Garrow's book, was often mocked behind his back for "talking black but sleeping white" because of his white wife.

A mutual family friend also confirmed that Obama tied his decision to dump Jager to her race.

"The lines are very clearly drawn … If I am going out with a white woman, I have no standing here," the friend recalled Obama saying.

Things supposedly came to a head at a summer getaway when Obama and Jager spent an entire afternoon loudly arguing about the issue within earshot of their friends.

"‘That's wrong! That's wrong! That's not a reason,' they heard Sheila yell from their guest room, their arguments punctuated by bouts of makeup sex," the Post reports.

Obama and Jager soon broke up, heading their separate ways. They eventually ended up in the same neighborhood again when Jager accepted a Harvard fellowship, but by that time Michelle was in the picture. Jager tells Garrow that the last time she heard from Obama was a phone call she received, asking if she was talking to any biographers.