Stephen Norris, two-time Conservative candidate for London mayor, is unlikely to stand again in order to make way for someone from a more diverse background.
Stephen Norris: Twice disappointed
He told GMTV he may give up his mayoral ambition for leader David Cameron, who wants more minority candidates.
The party plans to ask Londoners to choose their official candidate this autumn for 2008's mayoral election.
"Would I fall on my sword for young Dave? Yeah, actually I probably would," said Mr Norris.
"I do want the party to succeed and I am a huge supporter of David Cameron," he told GMTV's Sunday programme.
"I happen to think the drive to present a different kind of image of the party is absolutely what we need to do.
"And to people who say 'but this is about positioning, it's not about policy', I say you've got to be in the position first and that's exactly what he's achieving."
Mr Norris stressed that he had yet to make up his mind. But he predicted that Labour's incumbent Ken Livingstone - who has twice beaten Mr Norris to the job - would lose: "I think the magic went".
He came second in 2004 and 2000
Mr Cameron announced in June that the party would give Londoners a say on the Tory candidate. The process, similar to a United States-style primary, will involve hustings and then text and phone voting.
London-based party members can put their names forward to be candidates and head-hunters will also be used.