Ex-chancellor Ken Clarke has launched his bid to be the next Conservative leader saying he is "popular" enough to get the party back into power.
Mr Clarke, 65, posed for photos with backers including MPs Tim Yeo, Ann Widdecombe and John Bercow.
He is due to set out his plans for the party during a speech on Thursday.
It is the Rushcliffe MP's third attempt to win the Tory leadership - his pro-euro views were blamed for his defeats in 1997 and 2001.
He now says his enthusiasm for UK euro membership has cooled.
He told the Daily Mail on Wednesday that the issue was not a barrier to him leading the party.
"I said that the question of Britain's admission wouldn't arise for at least 10 years.
"That's not controversial, it's pure blind obvious. I don't think we're going to have any more silly arguments about treaties and constitutions. The constitution is dead."
Mr Clarke's potential rivals include shadow cabinet ministers David Davis, David Cameron, Liam Fox, Andrew Lansley, Theresa May and David Willetts.
Sir Malcolm Rifkind, who unveiled his own four-strong campaign team of MPs, welcomed the news, saying it was important the party should have the "broadest spectrum of choice" when deciding who the leader should be and said he too would be a candidate.
"I think it is very important that the Conservative Party should have a choice of a candidate who represents the One Nation tradition of the Conservative Party, which I do, but who also is opposed to the single currency and of moves towards a European federal state," he said.
Tory frontbencher Oliver Letwin played down the fact Mr Clarke is already well known among voters saying that whoever won the leadership contest would be exposed to huge amounts of publicity.
He said he believed Mr Cameron had the makings of a "great leader" and was "most likely to capture the hearts and souls of the people of this country".
But former Home Office minister Ann Widdecombe, who backs the ex-chancellor, said: "Either we are serious about being in government or we are not. If we are we must go for Ken Clarke."
Some of Mr Clarke's critics argue he is too old for the job and reluctant to change his mind on key issues.
But he told the Daily Mail: "At the next election we are talking about fighting Gordon Brown. I am as capable of doing that as I have ever been."
He added that he was determined Britain should be governed better than it had been under New Labour.
Sir Malcolm Rifkind was foreign secretary under John Major
"I am horrified by a government run on a basis of spin. The political health of Britain has deteriorated very sharply. The Conservative Party must do something about it, and I am the man to do it."
Mr Clarke lost out on the leadership to William Hague in a vote of MPs in 1997 and in 2001 he came second to Iain Duncan Smith in a run-off decided by grass roots Tories.
Current Tory leader Michael Howard announced his intention to stand down following May's general election defeat.
At the moment party members across the country choose the leader from a shortlist of two provided by Tory MPs.
But MPs want the final say to return to them, with grass roots party members consulted only on their preference. The result of a vote on whether to change the leadership election rules is due on 27 September.
If the rules are changed a new leader is likely to be in place by mid-November. If the rules are not changed the result is not expected until early next year.
However, in a letter to the Daily Telegraph a series of key figures representing rank and file Tories said the planned rule change should be rejected.
They point out that Tory MPs predominantly represent the shires and south east of England while there is "virtually no representation from the north of England, Scotland, Wales, the cities and more importantly women and younger people".