The 36-year-old former secretary of state for Wales could now attract votes from left and right, as the only candidate with the bandwagon potential to unite the party.
In yesterday's leadership bout, John Redwood - another former secretary of state for Wales - stunned colleagues by getting more votes than either of the other right-wing candidates, Peter Lilley and Michael Howard.
Barring surprises, it now looks as though Mr Clarke, Mr Hague and Mr Redwood will go through to next Tuesday's second-round ballot of the party's 164 MPs. Within minutes of the result being announced in a Commons corridor, Mr Redwood paged his campaign team with the message: "We're going all the way. JR."
Mr Clarke came top of the first-round ballot, with 49 votes, but he was only a handful of votes ahead of Mr Hague, on 41. Mr Redwood came third, with 27, followed by Mr Lilley on 24, and Mr Howard on 23.
The combined total of 74 votes for the three right-wingers is not enough to secure victory for Mr Redwood, who requires at least 83 votes next Tuesday.
In an appeal for Mr Howard and Mr Lilley to stand down, and unite behind him for the next round, Mr Redwood told BBC Radio 4's PM programme: "Both Michael and Peter or their camps indicated that they thought the fourth and fifth-placed candidate should drop out and support the third-placed candidate."
But it is entirely possible that MPs from the Lilley and Howard camps will now begin to peel off in search of a winner - Mr Hague.
There were Tory fears last night that some right-wing MPs could make a tactical switch to Mr Clarke, in the hope of keeping division, and the leadership question, alive. Other MPs believe that if Mr Clarke is not elected, there is no place for them in the party, and they could resign the party whip.
Last night, however, there was everything for Mr Hague, Mr Clarke and Mr Redwood to fight for.
Mr Hague said he had been pleased by his vote. "It gives me a very good position to campaign for the second ballot on a platform to unite the party and give the party a fresh start," he said.
Having topped an opinion poll, and a ballot of constituency party officers announced in advance of yesterday's vote, Mr Clarke said: "I have today topped the poll in every test of Conservative opinion. I am very encouraged by the breadth of the support I have attracted, which is much stronger than I dared to expect when this campaign started. The Conservative Party should now unite to fight Labour. I intend to seek to broaden my appeal further by setting out how I intend to lead this party on an inclusive basis. The leadership of the party must attract and draw on the talents of every strand of opinion within the Conservative tradition."
Mr Redwood said: "I am very pleased and I would like to thank all those who supported me even when the press wrote me off and down and out. Now we are going to have a bandwagon. Now we are going to win." He added that he would be "very generous" to Mr Lilley and Mr Howard. "I want them to be on side. I want as many supporters as possible."
The former deputy chairman of the party, Lord Archer, who had been backing Mr Lilley, said: "I believe that both Peter Lilley and Michael Howard will make their own decisions as to what they will do but neither of them can win."
That view had earlier been underscored by the result of an advisory ballot of constituency party officers, which gave Mr Clarke 322 votes, Mr Hague 188, Mr Redwood 25, Mr Lilley 22, and Mr Howard just 10. But it was noticeable that while Mr Clarke won a majority of the constituency votes cast, Mr Hague still got about a third.
Remarkably, only 61 per cent of Tory peers bothered to vote at all, but Mr Clarke got 177 of their votes to 45 for Mr Hague, 37 for Mr Lilley, 13 for Mr Redwood, and 10 for Mr Howard. All 17 Members of the European Parliament backed the former chancellor.
The Commons was last night rife with rumours of backstairs deals and offers. Mr Redwood said of Mr Howard and Mr Lilley: "If Michael and Peter would like jobs in the shadow cabinet that I wish to form, yes, of course they can have jobs."
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