The Prime Minister still has more cards than his critics — just. It is very hard to oust prime ministers. Incumbency gives them the initiative and requires challengers to stake their careers on the chance that they will succeed. That is why so few PMs have been forced out between elections. Even the aged Winston Churchill carried on for much longer than most of his Cabinet wanted. Of the 13 who have resigned, rather than been voted out of office, almost half went because of ill health or age.
Balfour jumped as his party split before electoral defeat; Asquith and Chamberlain went during wartime crises; Lloyd George was rejected by most of his coalition allies; an already ill Eden quit after the Suez fiasco; and