US presidential candidates Joe Biden and Donald Trump face off on Thursday in the first of two debates ahead of November’s razor-close election, with both aiming to use the 90-minute duel to win over crucial undecided voters. The contest is a rematch of 2020, when the world was in the depths of the Covid-19 pandemic. Four years later, the US is roiled by bitter fights over immigration policy, abortion rights, the pain of inflation, and Trump’s myriad of criminal cases, including his attempt to overturn Biden’s win in the last election. Foreign policy could feature prominently in the clash host…