About twenty five per cent of Democratic primary voters remain rational and do not want to vote for a bizarre open borders/socialist/ globalist who will destroy the American nation. Their only real choice in the democratic field is the 1980’s wok model Biden. However he is a brain damaged fossil and probably will not survive the primary process. Come November 2020 given the choice of a radical socialist/globalist or Trump, many will stay home or vote for Trump.
Or get Biden in with Harris as VP then resign