NEW YORK (AP) — A young civil rights activist named Bernard Sanders was arrested and dragged off to jail for protesting school segregation on the South Side of Chicago in the summer of 1963.

Most voters didn’t learn about that episode until photos surfaced in late February 2016, almost 10 months into the Vermont senator’s first presidential campaign. Sanders had been struggling to win over African-American voters, but his topsy-turvy campaign team didn’t know such powerful evidence of his civil rights bona fides existed until five days before South Carolina’s primary.