OPINION:
This time we really are in the endgame of the Boris Johnson premiership, but that still does not mean it will be quick. The prime minister has enjoyed an almost miraculous ability to defy political gravity but the co-ordinated resignation of both his chancellor and health secretary looks like the final fall to earth.
Johnson's instinct will be to hold on. Other cabinet ministers were quick to state their loyalty. Liz Truss, the foreign secretary was an early pledger. Without a change to the leadership election rules, there is no formal lever to force Johnson out. The prime minister would have to resign and he is going to spend the next hours working out how he can avoid doing so. The temptation will be to play to the party right by depicting this as a coup to weaken Brexit or, given the comments on economic differences in Rishi Sunak's letter, to keep taxes high.
While the resignations are a huge blow, they are not enough to suggest that he has lost the confidence of his cabinet. Many have a strong incentive to stay loyal until they are sure the ship is going down. A number know they are unlikely to be kept on by any other leader. Others, such as Truss, who harbour leadership ambitions will be calculating that their prospects are better served by not being associated with Johnson's dispatch. But this mini-cabinet coup will also turn demands for a change to the leadership rules into a central issue in the looming elections for the backbench 1922 Committee executive.
But whether the end now comes rapidly or is more drawn-out, it is hard to see any way back for Johnson. Premiers routinely survive cabinet resignations but these go to the issue of the fundamental character of his government and will confirm the sense of decay in Downing Street. It is now very hard to see him leading his party into the next election. The question now is how protracted the death throes have to be. Under existing party rules he technically has 11 months to turn it round but it is not clear what he can offer his MPs as a reason for keeping him. Some doubt he will make it to the end of this month.