Senator Bernie Sanders, a prominent figure of the US political left, on Saturday voiced support for Joe Biden’s presidential candidacy despite calls for him to withdraw over health concerns.

“Enough! Mr. Biden may not be the ideal candidate, but he will be the candidate and should be the candidate,” independent senator Sanders wrote in a New York Times column, adding that “it’s time for Democrats to stop the bickering and nit-picking.”

Sanders’ column comes amid steadily growing calls from Democratic officials and donors for the 81-year-old Biden to step aside following a disastrous performance in his June 27 debate with former president Donald Trump. So far, some 20 members of Congress have called for him to leave the race.