The Conservative Party leader, Michael Howard, made an unexpected appearance at a meeting of more than 1,000 party volunteers yesterday to warn them that blocking the rules could threaten party unity and discipline. But opposition to the rule change has hardened since Ken Clarke's entry into the contest last week, because of fears that his chances would improve if the change goes through.
A survey of 100 constituency association chairmen in today's Sunday Telegraph shows that 44 intend to vote against the rules - easily enough to block it.
"Choosing a leader who does not command the support of a majority of MPs is not the best way of achieving the discipline and unity we need," Mr Howard said yesterday.
"That is what you risk doing under the present system, in which a minority of MPs could combine with a majority of the rest ... to impose a leader the majority of MPs don't want."
Two rival leadership contenders, Liam Fox and David Willetts, have called for the rule change to be rejected. Party officials fear they cannot achieve the necessary two-thirds majority. This could mean that the contest will drag on into 2006.
Mr Clarke's supporters claim he will fight to win, whatever the rules. They have been buoyed by more than 1,000 messages of support on the new Clarke website within 48 hours of his campaign launch.
The former chancellor has brushed aside suggestions that, at 65, he is too old to take on the leadership - although if he won a general election, he would be the oldest Prime Minister since Alec Douglas-Home, 40 years ago. In 2001, Mr Clarke topped the poll among Tory MPs, but was heavily defeated by Iain Duncan Smith in a ballot of the party's membership. His supporters claim he can win, even under the 2001 rules.
The Clarke bandwagon was given a further push yesterday by Lord Patten, the former party chairman who engineered the last Tory election victory, in 1992. He told the BBC: "There are two questions - who would Mr Blair and Mr Brown least like to be leader of the Conservative Party? Secondly, who would the electorate most like to lead the Conservative Party? There is only one answer ... Ken Clarke."
Mr Clarke's third attempt at the leadership was launched with a professionalism and a degree of planning that confounded those who thought he was too disorganised to run a proper campaign. His team set up an interview with the Daily Mail, which backed Mr Clarke in 2001 despite disagreeing over Europe. It also arranged a photocall outside the Commons with seven MPs who are backing Mr Clarke, including the former Home Office minister Ann Widdecombe and Tim Yeo, a member of the Shadow Cabinet.
Ten volunteer workers moved into the Clarke campaign headquarters and set up the www.kenclarke.co.uk website. Supporters have been asked to email the site if they agree with the proposition that "it's time for the Conservative Party to win again, and Ken Clarke is the man to lead us to victory".
Opponents say Mr Clarke cannot put up a credible challenge to the frontrunner, David Davis. He was backed by 59 MPs in the final ballot in 2001, but 24 are no longer MPs or have backed rival candidates.
Out of 68 MPs who have declared themselves so far, 29 back Mr Davis, 12 are for David Cameron, 10 for Mr Clarke, eight for Liam Fox, five for Sir Malcolm Rifkind, and four for David Willetts.Reuse content