Supporters of Conservative leadership contender Ken Clarke have launched a "stop Cameron" campaign.
They are encouraging followers of David Davies to stick with their candidate rather than switching to David Cameron.
It follows a disastrous week for Mr Davies, the shadow Chancellor and former favourite to win the Conservative leadership race, who delivered a lacklustre speech at the Tory Conference last week.
By contrast, Mr Cameron, the shadow Education Secretary, impressed delegates and established himself as a serious contender in the leadership contest.
But followers of Ken Clarke, the former Chancellor, have been stressing that Mr Cameron, aged 39, lacks experience.
One Westminster source said: "Some MPs will never vote for Ken so Ken's supporters are encouraging them to stick with David Davies and let Ken take second place, rather than giving more votes to David Cameron and possibly pushing Ken down into third."
Conservative MPs will take part in the initial ballots and the two most popular candidates will then be put to a poll of the party membership.
Mr Davies will today set out his plans for Government in an article, in a bid to breathe new life into his struggling campaign.
The contenders have seven days to present their case, with the first round of voting scheduled for a week today.
Sources in the Davies camp have denied claims he has ditched his close ally Andrew Mitchell, MP for Sutton Coldfield, as a key campaign manager.
Reports at the weekend claimed that Mr Mitchell was to play less of a high profile role, while supporters such as Julie Kirkbride, MP for Bromsgrove, would present a softer face. But a Davies source said: "That's just rubbish."
Ms Kirkbride said: "David's strengths are his determination, his courage and his ability to unite the party." Supporters of Mr Davies - known as 'DD' to his followers - also point out that he never claimed to be a great orator and MPs have already given him their backing knowing this.
He remains the candidate with the most declared backers among Tory MPs.