Joe Biden's backing drops by third in new polls after debate clash with Kamala Harris

Support for Joe Biden’s presidential bid has dropped by a third after he was repeatedly challenged in the first debate between Democrats seeking the party nomination for the next US election, according to two polls.  The proportion of Democrats who said they would back Mr Biden, the former US vice president, to be their party's candidate in 2020 dropped from 32 per cent in May to 22 per cent according to a CNN poll.  That was mirrored by a surge in support for Kamala Harris, the