 Hello and welcome to NewsHour from the BBC World Service. We're coming to you live from London. My name's Paul Henley. Last night's televised US election debate, the first of the campaign between Joe Biden and Donald Trump, was always likely to be pivotal. But such was the performance of the 81-year-old incumbent president that the overwhelming reaction comes today in the form of a question. Is it time to find another Democratic candidate? And many Democrats are the ones asking it.