Tory MPs will vote today on which of the remaining leadership contenders will go to the deciding ballot of the party's 300,000 grassroots members.
Whoever finishes last of the three remaining candidates - Mr Iain Duncan Smith, Mr Kenneth Clarke and Mr Michael Portillo - will be eliminated from the contest in what should be the third and final ballot of MPs.
Mr Duncan Smith, the Thatcherite shadow defence secretary, yesterday reinforced his position as the new favourite to succeed Mr William Hague after securing the backing of former party chairman Mr Michael Ancram.
In contrast, Mr Portillo, the pre-contest favourite, has seen his hopes fade, despite finishing top in the first two ballots.
He has since struggled to attract support from the Davis and Ancram camps and there has been growing speculation at Westminster that could be overtaken today by both Mr Duncan Smith and Mr Clarke.
The shadow chancellor has had to endure a difficult few days, with accusations from former Tory spin doctor Ms Amanda Platell that his supporters were plotting against Mr Hague in the the general election campaign. Moreover, Baroness Thatcher has fiercely denied she was now backing him.
Many MPs believe Portillo's perceived liberal views on cannabis legalisation, scrapping Clause 28 - which bans the promotion of homosexuality in schools - and all-women shortlists for Conservative parliamentary candidates will finally put paid to his leadership hopes.
Mr Clarke said he could still finish in the top two but conceded it was now effectively a battle between himself and Mr Portillo to avoid elimination.
PA