David Cameron has left the door open to a deal with Ken Clarke in the race to succeed Tory leader Michael Howard.
A Cameron/Clarke alliance was touted earlier in the summer
Mr Cameron, 38, was asked on BBC Radio 4's Today programme about a possible "dream ticket". He replied: "I certainly don't rule anything out."
Mr Clarke, 65, who Mr Cameron said was a "huge figure" in Tory politics, says he will run if he thinks he can win.
The ex-chancellor would be expected to take the senior role in any alliance with the shadow education secretary.
Mr Howard said he would quit as Tory leader later this year after he lost May's general election to Labour.
Since then a series of potential candidates have been setting out their visions for the Conservative Party, which has been in opposition since 1997.
Potential candidates also include Liam Fox, David Willetts, Theresa May, Sir Malcolm Rifkind, Andrew Lansley, Tim Yeo and David Davis, who is the bookmakers' favourite.
Mr Cameron told Today: "I am putting forward my ideas and my approach talking about a modern, compassionate conservatism. And if people like my ideas then I should put my name forward. If people like Ken's ideas he should put his name forward."
The rules will not be finalised for the leadership contest until late next month, although Conservative MPs have already voted for a system where they, rather than party members, get to choose the leader.