Barack Obama is returning to the Democratic National Convention stage two decades after his memorable debut. His job is different this time. In 2004, Obama was a young state senator from Illinois stumping for nominee John Kerry and introducing himself to the nation. That speech came months before his election to the U.S. Senate and catapulted him on a course to the presidency barely four years later. This time, Obama is the 63-year-old elder statesman eight years removed from serving two terms as the nation’s first Black president. And he will be making the case for another historic figure: Vice President Kamala Harris. Democrats say they expect Obama to balance aggressive attacks on Republican Donald Trump while boosting Harris.