Barack Obama, the 44th US president and a marquee name in Democratic politics, is due to take to the stage in his adopted home town of Chicago to address the party faithful on Tuesday evening. He is expected to pay tribute to outgoing President Joe Biden, who served as Obama’s vice president for eight years, and use his well-known rhetorical powers to deliver a thundering endorsement of Democratic presidential nominee, Kamala Harris. Obama, who got his political start in Chicago, has kept a low profile since leaving office in January 2017. But he remains a broadly popular public figure and one…