Sir Michael, a 51-year-old company director, is the clear front-runner after it was confirmed by the party yesterday that Michael Forsyth, the Secretary of State for Scotland, would not abandon his marginal Stirling constituency for the Eastwood safe haven - a predominantly middle-class dormitory to the south of Glasgow.
Mr Stewart's resignation late on Monday evening left Scottish Tories temporarily stunned and delivered a jolt to John Major just hours after he had at last taken the election initiative over the economy.
Mr Stewart's decision followed weekend press reports linking him with a 47-year-old married woman he met last year at a clinic for treating alcohol problems. Catherine "Bunny" White, who has four children, was said to have stayed at the MP's London flat.
Last Sunday, Mr Stewart, 54, posed for photographs with his wife Susie at their home in Neilston, Strathclyde, but refused to discuss Mrs White. An MP since 1979, he stepped down as a Scottish Office minister after a confrontation with road protesters on the site of the M77 led to a pounds 200 fine for breach of the peace.
Expressions of sadness by his parliamentary colleagues quickly gave way to speculation over a successor. Mr Stewart had the biggest Conservative majority in Scotland in the 1992 election - a comfortable 11,688 votes.
Constituency officials described as "preposterous" a suggestion that Mr Forsyth might try and switch to Eastwood. A swing of only 0.3 per cent to Labour would deprive the Secretary of his Stirling seat.
Two other Cabinet ministers, Malcolm Rifkind and Ian Lang, also face tough battles, but party officials in Edinburgh said they did not expect any sitting MP to apply for Eastwood.
In a succession of interviews yesterday, Sir Michael repeatedly avoided ruling himself out - other than a frank admission that if the constituency association wanted "a bright young thing" then he was not in the running.
If Sir Michael was selected, however, it would leave the Tories with a further headache, since as party chairman he is responsible for co-ordinating the election campaign in Scotland.Reuse content