The limousine carrying President John F. Kennedy races toward the hospital after he was shot in Dallas on Nov. 22, 1963, with Secret Service agent Clint Hill riding on the back. Justin Newman/AP hide caption

itoggle caption Justin Newman/AP

Health and Human Services Secretary Kathleen Sebelius speaks Thursday in Phoenix. Laura Segall/Getty Images hide caption

itoggle caption Laura Segall/Getty Images

Democrat Terry McAuliffe (left) and Republican Ken Cuccinelli talk before a debate in the Virginia gubernatorial race, last month in McLean, Va. Linda Davidson/The Washington Post/AP hide caption

itoggle caption Linda Davidson/The Washington Post/AP