US Democrats gather in Chicago this week for the party’s national convention, with Vice President Kamala Harris set to formally accept her nomination as candidate for president in November’s election. The four-day meeting, which opens on Monday, is set to crown Harris and running mate Tim Walz as the Democratic Party’s choice to face Republican nominee Donald Trump, less than one month after 81-year-old President Joe Biden dropped his bid for a second term as his age and mental capabilities came under growing scrutiny. Biden, who said he was ready to “pass the torch” to younger Democratic Part…