The day after Barack Obama became the first African-American president of the Harvard Law Review in 1990, he took a phone call from Sheryll Cashin, then a law clerk to Judge Abner Mikva of the U.S. Court of Appeals for the D.C. Circuit.

Mikva by then was a “feeder judge” for Supreme Court law clerks, and Cashin told Obama that Mikva was “very interested in you,” according to a new biography of Obama’s life before becoming president in 2009.