With just three weeks left until Conservatives choose their next leader, the two contenders yesterday launched their mini-manifestos pledging to unite the party and steer a course for electoral victory.
As ballot papers were sent out to more than 300,000 party members across the country, the pro-euro, Mr Kenneth Clarke appealed to party members not to concentrate on Europe and said he would establish special commissions to discuss key policy issues on health and education.
His rival, Mr Iain Duncan Smith, insisted he would "settle" the idea of Europe as a divisive issue and would be "tolerant" of pro-euro campaigners.
The Eurosceptic, Mr Duncan Smith, launching his manifesto in Bradford, hit the ground running when he pledged to "lead from the front" by voting against the Nice Treaty in the Commons in October.
Mr Clarke's critics attempted to contrast his "clear leadership" stance with Mr Clarke's earlier admission that "diary commitments" meant he would not be present for the vote as a sign that he was not fit for leadership. But the Clarke camp hit back in sisting he "doesn't have a problem" with the party's opposition to the Treaty, but simply couldn't be present for the vote.
A spokesman told The Irish Times that Mr Clarke believed the Treaty was "badly drafted" but Labour's majority in the Commons meant the vote would be easily won.
Mr Clarke, whose campaign has been endorsed by the party's vice-chairman, Mr Steve Norris, and the shadow cabinet office minister, Mr Andrew Lansley, within the last 48 hours, also dismissed reports that several right-wingers would leave the party if Mr Duncan Smith failed to secure the leadership.
"I think the Conservative Party has had quite enough of people throwing their toys out of the pram if they feel at the moment they are not in line with the main view of the party. Anybody from either wing of the party who says they are going to leave if they don't like the leader is free to go because that particular instinct is the kind of thing that has been undermining the party for the last 10 years," Mr Clarke said as he launched his manifesto at Westminster.
With Europe continuing to dominate the leadership race and the Clarke camp emphasising that his appeal reaches beyond his Euroscepticism, Mr Clarke produced a list of 12 MPs who have joined his campaign.
The "Eurosceptics for Ken" group includes the shadow home secretary, Ms Ann Widdecombe and the former foreign secretary, Sir Malcolm Rifkind.
In another favourable development, 60 business leaders pledged their support for the former Chancellor.
In a letter to the Financial Times, the group, including the chairman of British Midland, Sir Michael Bishop, said they held various views on the euro but were supporting Mr Clarke because he had "unparalleled experience in managing Britain's economic and social affairs."
There was also an invitation to the shadow foreign secretary, Mr Francis Maude and the former favourite in the race, Mr Michael Portillo, to join the Clarke camp.
Mr Maude warned at the weekend that Tories risked slipping into third place behind the Liberal Democrats if they did not adopt the inclusive agenda promoted by Mr Portillo. Inviting both men to join him in his policy commissions, Mr Clarke said he wanted their help to win the next election.
In his manifesto Mr Duncan Smith promised to reduce taxes and support the so-called "Star Wars" missile defence system saying Britain should join its allies to protect the world from "unstable states obtaining weapons of mass destruction."
Mr Duncan Smith received a huge boost when Baroness Thatcher declared she was backing his bid to become the next leader of the Conservatives.