Four days after taunting Tony Blair with, "You were the future once", the new Conservative leader was lifted by polls showing the Tories have edged ahead of Labour by two points.
However, Ken Clarke, a defeated leadership contender, threatened to open up the first split with the new leader over Mr Cameron's decision to adopt a "head-banging" policy by pulling the Conservative MEPs out of the right-wing grouping, the European People's Party, in the European Parliament.
Mr Clarke, who was appointed head of the democracy task force by Mr Cameron, warned it would make Mr Cameron the most extreme Eurosceptic ever to lead the party.
"I hope he will take many months over his decision on the European Parliament and perhaps decide that being a more extreme Eurosceptic than any of his predecessors is not the best way to launch himself on the international scene," Mr Clarke told the BBC's Politics Show. " Given all the goodwill that's surrounding his taking over, and the optimism everybody has for him, what a pity to insist on finding some new, slightly head-banging European policy, Eurosceptic position, to take up as his first act in the leadership."
A senior Tory spokesman said: "We know this is Ken's view. There is nothing new in that."
Mr Cameron will use his poll boost to assert his authority for modernising the Tory party and will tell party faithful today that the failure of Conservative associations in the past to elect more women candidates has to change. Under his proposals, 70 winnable Conservative seats half of the Tories' 140 target constituencies will have to go to women and all other selections will be frozen.
Some Tory MPs, such as Ann Widdecombe, have spoken out against plans for positive discrimination in favour of women. Tory activists claimed a survey of 767 members, which correctly predicted the outcome of the leadership election, found that only one third of Tory members support Mr Cameron's plans for an A-list of Tory candidates.
Mr Cameron will say: "Only if we engage the whole country in our party will our party develop ideas that benefit the whole country. The conversation we have in the Conservative Party must reflect the conversation in the country, and the sound of modern Britain is a complex harmony, not a male voice choir."
Theresa May, the shadow Leader of the House, who has championed the case for more women and black Tory candidates, said the moves would not produce " second-class MPs".
Mrs May said: "Associations will be expected to select from that A-list and I can't see any association saying 'well, actually we don't want the brightest and the best', because that's what it will be."
Bromsgrove MP Julie Kirkbride said: "The simple fact is there are more ex-soldiers than women in the ranks of the Conservative parliamentary party and that simply has to change."
Oliver Letwin, the chairman of the Conservative policy research department, said the polls showed the party had begun to reach out to millions of people who had not given it "the time of day" for the past 10 years.
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