Civil rights leader John Lewis on Thursday dismissed Democratic presidential candidate Bernie Sanders’ 1960s work on racial equality, saying, “I never saw him. I never met him.”

The Georgia congressman — a stalwart of the Freedom Rides through the South, lunch counter sit-ins and the 1963 March on Washington — raised questions about Sanders’ involvement in the movement when the Vermont senator was a college student.

Lewis endorsed Sanders’ chief rival, Hillary Clinton in October and is expected to campaign for her in the days approaching the South Carolina primary, according to Talking Points Memo. His comments come at a critical time as the two White House contenders focus on the upcoming primaries in Southern states with predominantly African-American Democratic voters. He made the remarks at a Capitol Hill news conference where members of the Congressional Black Caucus’ political action committee delivered a full-throated endorsement of Clinton.

On his campaign website, Sanders says he has a “long history of fighting for social equality and the rights of black Americans — a record that goes back to the early 1960s.” While a student at the University of Chicago, Sanders was involved in the Congress on Racial Equality and the Student Nonviolent Coordinating Committee. He also was arrested while protesting segregation.

“I never saw him. I never met him,” Lewis told reporters. “I chaired the Student Nonviolent Coordinating Committee for three years from 1963 to 1966. I was involved in the sit-ins, the Freedom Rides, the March on Washington, the march from Selma (Alabama) to Montgomery and directed the voter education project for six years. I met Hillary Clinton, I met President Clinton.”