Under these conditions, he said Mr Johnson would become “an election asset for the opposition”.
The most pertinent threat against the PM is, at present, his own party members.
So far, six have publicly entered letters of no confidence, 54 of which are required to trigger a vote.
Others may have handed theirs under the radar, as a group of 12 2019 intake MPs reportedly operated a “pork pie plot”.
Once MPs cross the agreed threshold, they need a total of 180 to vote Mr Johnson out.