Theresa May is racing towards victory, with most Conservatives backing her to replace David Cameron, polling has revealed.
Bitter recriminations over rival Michael Gove's decision to pull the rug from under Boris Johnson's leadership bid appear to have dented his prospects of taking on the Home Secretary in the final vote.
The Justice Secretary faces being pushed into third place by fellow Brexit campaigner Andrea Leadsom, whose support is growing.
Former City worker Leadsom has likened herself to Margaret Thatcher and praised the late prime minister's ability to mix toughness with "personal warmth". She told The Sunday Telegraph: "As a person, she was always kind and courteous and as a leader she was steely and determined.
"I think that's an ideal combination - and I do like to think that's where I am."
Gove has faced accusations of "treachery" since his decision to pull his support for Johnson and stage his own bid for the top job. He told the newspaper his confidence in the former London mayor had "evaporated".
"Over the past week, to my deep regret, my confidence evaporated. That led me to make the difficult decision, at no little cost, to put friendships aside and act in the national interest," he said.
With levels of support stronger than the combined total of her four rivals, May appears to be on course to take the keys to No 10. The Home Secretary was backed by 60% of Tory voters, with Gove second on 10 points and Leadsom on six, according to the ICM poll for The Sun on Sunday.
Among party members, who will vote to decide the winner of the leadership contest, some 46% say she would make the best prime minister. May has also been backed by more MPs, who select the final two candidates to go on to the ballot paper, than any of the other candidates.
Although the poll puts Gove, who has wider name recognition, ahead of Leadsom, bookies have slashed the odds on the junior minister making it through the knock-out stages in Parliament to go up against May in the head-to-head.
The first round of voting to whittle down the field of runners is being held on Tuesday. More than half of those polled - 55% - by ICM were unable to give any view on Leadsom or Work and Pensions Secretary Stephen Crabb, who have lower profiles than the long-standing Cabinet ministers, and 42% had the same problem with former frontbencher Liam Fox.
Details emerged of a speech Leadsom made three years ago, saying leaving the EU would be a disaster.
According to the Mail on Sunday, she told the Hansard Society's Annual Parliamentary Affairs Lecture: "I'm going to nail my colours to the mast here: I don't think the UK should leave the EU. I think it would be a disaster for our economy and it would lead to a decade of economic and political uncertainty at a time when the tectonic plates of global success are moving.
"Economic success is the vital underpinning of every happy nation. The well-being we all crave goes hand in hand with economic success."