"African American superdelegates previously pledged to Clinton, found themselves under pressure to switch to supporting Obama's candidacy; one example being John Lewis, a noted leader of the Civil Rights Movement, marcher in the Selma to Montgomery marches, US Representative from Georgia, and superdelegate, who formally switched endorsements to Obama on February 27, 2008; Representative Jesse Jackson, Jr. suggested that those staying with Clinton might face Democratic primary challenges in the future.