evidence: US President-elect Joe Biden has picked veteran political operative Ron Klain to be White House chief of staff. Mr Klain has served as a top aide to Mr Biden since the 1980s in the Senate and later when he was vice-president. [...] Mr Klain served as chief of staff to Mr Biden from 2009 to 2011, the first few years of Mr Biden's tenure as vice-president in the Obama White House.