Starmer saying Corbyn would have been a better PM than Johnson is a serious blunder which could do real damage to Labour’s campaign.
However awful, dishonest, incompetent etc etc Johnson was, at least he wasn’t a threat to U.K. national security, unlike Corbyn.
The idea of Johnson as PM appalled me, but the idea of Corbyn as PM genuinely frightened me. He would have been hopelessly & dangerously out of his depth from day 1 and would have been incapable of making the decisions necessary to keep this country safe. The idea of Corbyn dealing with Putin or Xi Jinping just doesn’t bear thinking about.