Washington (AFP) – Former US vice president Joe Biden has opened up a 16-point national lead over President Donald Trump less than a month before the November 3 presidential election, according to a CNN poll published on Tuesday.The Democratic presidential candidate leads the Republican incumbent by 57 percent to 41 percent among likely voters, according to the nationwide CNN poll conducted by SSRS.The survey of 1,001 likely voters was conducted between October 1-4, CNN said — after the presidential debate and mostly after Trump tested positive for coronavirus.It has a margin of error of plus…