Speaking at a packed fringe meeting staged by The Independent in Blackpool, the former Chancellor tried to calm the nerves of Eurosceptic Tories who are worried about his pro-European views.
He won a warm response from activists who crammed into the Baronial Hall at the Winter Gardens, which suggested grassroots members are swallowing their previous doubts about him. As they left the meeting, several doubters said he had done enough to win them round.
Although he was rejected by Tory members in favour of Iain Duncan Smith in 2001, the Clarke camp is increasingly confident he can win their backing - but must first secure a place on the shortlist of two names to be chosen by Tory MPs.
Mr Clarke warned his party it would be wrong to make Europe the dominant issue of the leadership election, since the single currency and the proposed EU constitution were now off the agenda. If it did, the party would be having the same debates on Europe in a three or four years' time "but we won't be in government, that's for sure", he said.
Mr Clarke promised that the overwhelming majority of his Cabinet would be Eurosceptics if he became Prime Minister. He dismissed as "a tall order" the idea that he had a secret plot to turn them all into Europhiles so that he could take Britain into the single currency. He declared: "If you think I have gone through all this process to try and become Prime Minster in four years time to see the whole blasted thing exploded when I destroy my political base by trying to take us into the single currency I can only assure you that is a paranoid fear."
He dismissed speculation in Tory circles that Labour would seek to exploit Tory divisions over Europe if he became leader by bringing forward initiatives on the issue.
An unabashed Mr Clarke told the fringe meeting that his CV showed he was the best qualified of the five candidates, adding that the "clearly expressed" view of the public was that he was the most popular. Urging the Tories not to elect another Leader of the Opposition but a potential Prime Minister, he said that if the party lost the next election it would not die but would "settle down as a right-wing party of opposition".
Mr Clarke argued that campaigning on "hard issues" such as crime and immigration at the May election rather than the economy, health and education had cost crucial support among women.
Denying that at 65 he was too old to lead the Tories, Mr Clarke pointed out that the Pope is 78 and Gladstone was 82 when he became Prime Minister. "I don't seem to suffer from stress. I quite enjoy it all," he said.
The former Chancellor admitted there could be a hung parliament after the next election. "I rather dread that. I don't like coalitions," he said. He suggested it would be "a pretty bad spell" of government.
He criticised the Tory proposal at this year's election to subsidise people paying for private health treatment but dismissed the idea that he was a conservative on public service reforms. "In the work of government, I am a reformer," he insisted.