The likelihood of a reshuffle before the summer recess has increased sharply not only because of continued speculation that Mr Major's leadership could come under pressure after the European elections, but also because the Scott arms-for-Iraq inquiry is not now expected to report until December.
There had been suggestions in Whitehall that Mr Major might have been tempted to wait until the early autumn to take account of any casualties resulting from the Scott report. But that strategy would now take him beyond November - the first opportunity of an outright challenge to his leadership.
The reshuffle will not be as savage as Harold Macmillan's notorious Night of the Long Knives in 1962, partly because of the risks of creating new and powerful opponents on the back benches, and partly because of clear indications that Douglas Hurd will stay for the rest of 1994 at least. That means the Cabinet's top three jobs are almost certain to remain unchanged.
Although the list of candidates for the Cabinet is limited, Stephen Dorrell, Financial Secretary to the Treasury, is a virtual certainty for promotion in the reshuffle. Brian Mawhinney (health), Jonathan Aitken (defence procurement), Sir George Young (housing), and Roger Freeman (transport) and David Davis, Cabinet Office, are also plausible candidates.
But Baroness Blatch, who has performed effectively at Education, and is close to the Prime Minister, is understood to have told him that she has no wish to enter the Cabinet. That has prompted an urgent search for an alternative peer who could lead the Lords in the absence of Lord Wakeham, who has indicated he may stand down. Suggestions last night that Lord Walker or Lord Howe would fulfil that role were being treated with some caution in Westminster.
A more acute problem is a shortage among Parliamentary Under-Secretaries of suitable candidates to go up a rung to Minister of State level. There are several ministers of state who are judged by party managers to have gone as high as they will get, or will want to go. Below that there is no shortage of parliamentary private secretaries and younger backbenchers due for promotion.
The possibility of a minister of state for the Prime Minister's office, and the appointment of a senior parliamentarian as a chief of staff, have both been canvassed as possible ways of beefing up Downing Street, where Graham Bright, Mr Major's Parliamentary Private Secretary, is deeply trusted by the Prime Minister but is seen as lacking in presentational skills.
David Hunt, Secretary of State for Employment, remains a frontrunner to be given the mixed blessing of the party chairmanship. One hotly contested suggestion in Whitehall is that his department could be scrapped at the same time.
The question of whom to dismiss is also problematic. Peter Brooke, Secretary of State for National Heritage, must be high on any possible dismissal list since his return to Cabinet was precipitated by the accident of David Mellor's resignation.
Tony Newton, Leader of the Commons, would remain loyal on the back benches but is highly regarded as one of the ablest leaders of the House for some time. John Gummer, thought unlikely to survive the last reshuffle, is seen as doing better at Environment.
John MacGregor is one possibility though he recently sought to quash reports that he intended to stand down. John Patten has many critics but has made some effort over the past year to broaden his appeal in the party. John Redwood irritates many colleagues, but his cleverness is not in doubt and as the most recent entrant would be a highly surprising - and dangerous - candidate for dismissal.