FILE - In this Aug. 28, 1963, black-and-white file photo, Dr. Martin Luther King Jr., head of the Southern Christian Leadership Conference, addresses marchers during his "I Have a Dream" speech at the Lincoln Memorial in Washington. President Barack Obama's presence at the ceremony, Wednesday, Aug. 28, 2013, celebrating the 50th anniversary of the March on Washington, will embody the dreams of the 250,000 people who rallied there decades ago for racial equality — and the continuing struggle by others for that goal. (AP Photo/File)