Voting is under way in the Conservative leadership contest after a televised clash between the two contenders, David Cameron and David Davis.
Ballot papers were sent out on Friday, leaving the 300,000 members around the UK a month to decide.
Odds on Mr Davis shortened for the first time since October's Conservative party conference after the hour-long BBC Question Time debate.
But Mr Cameron remains the bookmakers' favourite to land the Tory crown.
The candidates now go before a nationwide series of hustings.
'Coming from behind'
However, most members are expected to return their ballot papers well before the 5 December deadline.
Mr Cameron, 39, won the final vote by Tory MPs, who narrowed the candidates to two before the wider membership was given the final say.
Mr Davis told the BBC on Friday: "David's leading at the moment, at least the last numbers show that.
"I quite like that. I quite like coming from behind in these things."
He also said: "I wanted a highly principled approach, distancing ourselves from the Labour government. David had a different way, which he put rather differently."
A Cameron campaign spokesman hit back at suggestions Mr Davis had got the better of his younger rival in the televised contest, saying "David Cameron beat him on most questions."
He claimed Mr Davis had come into the debate looking "hopeless" and "incompetent" and had targeted his message at core Conservative supporters, while Mr Cameron tried to speak to the wider electorate and a "new generation" of voters.
A Davis campaign spokesman said it had been "inundated" with e-mails from new supporters following the Question Time debate.
He said Mr Davis had won the contest and was keen to take part in further televised clashes with Mr Cameron.
'Tough' drugs policy
During the Question Time debate, Mr Cameron, who has repeatedly been asked whether he took drugs at university, suggested that ecstasy could be downgraded, to help make policy more "credible" to young people.
David Cameron 1/10
David Davis 11/2
Source: William Hill
But on Friday his camp appeared to backtrack.
Mr Cameron's spokesman said the issue would be debated if he became leader, but added: "It would be a matter for the party to decide."
Mr Cameron later told a meeting in Winchester, Hampshire: "What people want is a realistic and sensible policy that gets to the bottom of the drugs' problem."
He wanted to see ex-addicts going into schools to talk about the dangers of drugs and tell of the difference between substances such as heroin and ecstasy.
Mr Cameron said that this was a "tough" drugs policy, adding: "Frankly I do not care what other people think about it."
During Thursday's debate, Mr Davis claimed his rival was focusing on spin rather than substance, but Mr Cameron countered by saying Mr Davis was setting policies to win headlines.
Mr Cameron said he wanted to set the general Tory direction now but not rush into details, concentrating on getting things right in the long term.
Mr Davis, shadow home secretary, argued the public needed to know what Tory policies would mean.