Shadow environment secretary Oliver Letwin has declared his support for David Cameron as the next Tory leader.
David Cameron is emerging as one of the main leadership contenders
Mr Letwin used an article in the Sunday Telegraph to hail Mr Cameron, 38, as a man with the "instincts", talents and beliefs to return the party to power.
The declaration by Mr Letwin, seen as an intellectual heavyweight, is a coup for "young pretender" Mr Cameron.
The shadow education secretary is fast emerging as the main leadership challenger to favourite David Davis.
It will increase his chances of establishing himself as the sole candidate of the party's centre-left to take on Mr Davis when leader Michael Howard steps down in the autumn.
In the article, Mr Letwin praised the "modernising" vision of a "civilised Britain" combining free markets with a stronger society put across by Mr Cameron in a recent speech.
The speech "established him in the front rank of British politics", Mr Letwin said.
He praised Mr Cameron personally, saying: "I hope that he will stand. If he does, despite my admiration for other friends and colleagues, I will back him."
Mr Letwin also praised other potential leadership contenders.
He singled out shadow trade and industry secretary David Willetts for his "thoughtful" argument that the Conservatives should be "at once a liberal party of free markets and a communitarian party that aims at the strengthening of society".
He acknowledged that Mr Howard's decision to delay his departure after announcing his resignation on 6 May had been "controversial".
But it had given the party an opportunity for "intelligent and much-needed constructive discussion" about its future, he insisted.
"All of this fills me with optimism about the future of our party," he said.
"We are thinking again - the first prerequisite for any political movement."