In his first speech for the Tory leadership contest, the former chancellor of the Exchequer said: "In opposition, the party organisation takes on a critical new importance. I believe we must overhaul and revitalise our organisation at every level, so that, just as it did for Labour under Blair, party reform becomes the instrument for the widest possible participation in a new Conservatism."
Mr Clarke told the Inns of Court Conservative Association, in London, that once the leadership election rules had been changed, towards the end of the year, he would resubmit himself for re-election under the new rules.
But as Michael Howard, the former home secretary, indicated in a speech to constituency Conservative association chairmen at a Westminster meeting last night, that is now becoming common ground among the candidates.
Mr Howard said: "I promise that if I am elected, I shall stand again for election under the new rules as soon as that can be arranged."
That opens up the prospect of the new leader standing down as John Major did in 1995, in order to defend his own leadership, early next year. But the incumbent has an undoubted advantage, and few believe the party at large would wish to oust a new leader so soon after his first election next month.
In his maiden campaign speech, Mr Clarke said last night that the economy would be the "absolute centre-point" of Tory attack on Labour, which, he said, was "preparing to cook the books which we left in apple-pie order".
But he warned that the most vital task faced by the Conservatives was to create a fighting machine that could win again. "The Conservative Party is a party of power, or it is nothing," he said.
That meant unity, and an end to in-fighting, but also creating "a positive, popular force which can reach out and appeal to those groups which the parliamentary party now under-represents: to women, to the young, to the cities, to Scotland and Wales".
Mr Howard told his meeting, however, that the Tories had been written off after the 1945 Labour landslide, but they almost got back five years later and Churchill was returned to office in 1951, "inaugurating 13 years of Tory administration. So, yes, we have a way to climb. But we are climbing Snowdon, not Everest".
Earlier, leadership contender John Redwood told a press conference that his own version of the "green" crusade meant more attractive public transport, without penalising car drivers, and a concerted programme to increase water supply through a curb on leakages.
Answering questions, he protested that he was not intent on taking the party to the right, but was running a mainstream campaign. "We don't want to run a faction," he said. "We want to run the Conservative Party as a whole in the interests of the wider electorate.
"I am fed up with all this right-left stuff. We are Conservatives. We believe in common-sense principles. It is high time we were proud of those principles and got out there and told people why we believe in them, why they would be good for them."