Vice president Kamala Harris and former president Donald Trump have gone head to head for the first time.     In a fiery 90 minutes, Ms Harris attacked the former president over his criminal convictions and the size of the crowds at his rallies, while Mr Trump doubled down on claims the Democrats had damaged the US economy.     Mark Austin is joined by US correspondent James Matthews from the floor of the debate hall for this episode of the Daily to go through the key moments from the debate, and look at the impact a surprise entry from pop mega-star Taylor Swift could have ahead of the election in November.     Audio credit: ABC News Presidential Debate    Producer: Soila ApparicioEditor: Philly Beaumont