US election: Barack Obama made his DNC debut 20 years ago. He's returning to make the case for Kamala Harris

Laying the groundwork Obama's two decades in public life have been defined by seminal speeches. His body of work features a range of tone and purpose - an array of choices as he seeks to strike the right balance for Harris as she tries to become the first woman, second Black person and first person of South Asian descent to reach the presidency.