The results of the ballot to be announced tomorrow will give Mr Clarke's bandwagon a huge heave by putting pressure on Tory MPs to back the former Chancellor in the secrecy of the first ballot.
William Hague is expected to come second in the ballot of Tory constituency chairmen, who will cast their votes by telephone using secret pin numbers.
The results, to be announced immediately before MPs vote, could increase the demands for a re-run of the election, if the MPs ignore the views of the constituencies and elect one of the outright Euro-sceptic right- wing candidates, Michael Howard, Peter Lilley or John Redwood.
The right-wing camps will meet after MPs vote tomorrow morning to thrash out a deal to stop Mr Clarke or Mr Hague, amid continuing speculation that Baroness Thatcher would prefer a more Euro-sceptic leader.
Mr Lilley called on the third and fourth candidates to drop out of the race for the second ballot, to avoid the right-wing vote being split. But in a move which could help Mr Clarke, Mr Redwood, the most outspoken opponent of European monetary union, said he intended to "go on" until he won the argument for ruling out the single currency.
Mr Clarke who is trying to convince the Euro-sceptics to vote for him, as a "big hitter" against Tony Blair, offered the right no concessions yesterday in his pro-European views. The ex-Chancellor, who last week called for delay of the single currency, on BBC Television's On the Record programme refused to commit himself to a referendum on the single currency beyond the lifetime of this Parliament.
All the camps yesterday were trying to talk-up their support. Mr Lilley and Mr Howard were believed to be neck-and-neck for third place.
Mr Clarke won the backing of the former cabinet minister, John MacGregor, while the Hague camp won the endorsement of Charles Lewington, former head of communications at the Conservative Central Office during the election.
Mr Lewington became the first "insider" to break cover over the election debacle, by writing in the Sunday Telegraph that John Major had admitted two weeks before the election that the Conservatives could not win and that frustration over the civil war in his party plunged the ex-Prime Minister into "black moods" and he would "lash out at those closest to him".
After Edwina Currie destroyed Mr Major's pre-election rally in Bath by urging him to quit early if the Tories lost the election, Mr Major told Mr Lewington: "I am sorry you have to deal with these people." After a pause, Mr Major added, "Sometimes I don't know why I bother."
Sporting Index, the spread-betting organisation, said Mr Clarke is ahead with punters betting on the ex-Chancellor getting 58-62 votes in the first ballot; Mr Hague 33-37; Mr Howard 25-29; Mr Lilley 21-25; and Mr Redwood 17-20.
The main movement in the past few days has been Mr Howard coming up to overtake Mr Lilley.Reuse content