WASHINGTON — President Joe Biden’s political world is collapsing. Top allies have either publicly or privately called on him to step aside. Major donations have fallen off a cliff. Grassroots fundraising is not keeping up with the demands of a campaign that needs to aggressively scale up three months before the presidential election. Members of his own re-election effort have already declared he has no path to victory. 

Since a disastrous debate in Atlanta upended the trajectory of his…