An Independent survey of the six campaign groups shows that more than one-third of the 164-strong electorate of Tory MPs has so far come out in support of a contender, with big-name sponsors such as Michael Heseltine being held in reserve.
Campaign managers want to "spin" out the announcement of high-profile backers, as the Labour Party did with its celebrity catches during the election campaign.
But The Independent has established that in addition to the six contenders - Mr Clarke, Stephen Dorrell, William Hague, Michael Howard, Mr Lilley, and John Redwood - 53 MPs have so far publicly declared their support.
In addition to that, there are another 27 whose support has been identified within the campaign groups but is being held back, either for tactical reasons or because the MPs do not wish their views to be made known to their local parties.
So far, Mr Clarke's campaign has the public backing of five former ministers, but his supporters say that they have identified the "certain" votes of another 41 MPs; giving him a total of 47 votes so far.
Under the first-round rules for 10 June, a candidate needs a majority of those entitled to vote - 83 - and a majority of 15 per cent of those entitled to vote - at least 25 votes - over the runner-up. As things stand, Mr Clarke is leading the field, but he falls short of the 83-vote hurdle.
However, his supporters believe that if he can get between 60-70 votes on 10 June, he could manage to get the extra votes needed to win a second- round ballot on 17 June, when 83 votes are required to win.
Certainly, the former Chancellor can expect the six votes that will go to Stephen Dorrell in the first round, but other camps doubt Mr Clarke's ability to make further headway.
If Mr Clarke does not get 60 votes in the first round, or if doubt sets in, then MPs are expected to start switching in search of the winner. At that point, Mr Lilley could begin to pick up significant support from across the party.
One potential eventual Lilley voter said yesterday that he was "John Major without the charisma", but he preferred him to the right-wing alternatives of Michael Howard and John Redwood.
William Hague, who began as an early favourite in the leadership race, appears to have badly blotted his copybook with his criticism of the "constantly shifting fudge" of John Major's leadership of the party. He is unlikely to be forgiven for that blunder - critical with an electorate that is "so small but perfectly formed".
The calculations being made by the different camps yesterday showed that there were possibly more than two dozen genuine "don't knows" or "won't says" left, with a further 10 MPs floating between candidates.
That critical mass of about three dozen MPs - including former ministers Nicholas Soames, Alan Clark, Cheryl Gillan, David Heathcoat-Amory, and Robert Key, not to mention John Major - will decide the result. But for the moment, no one knows where they are heading.
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