Sir Vince Cable is set to become leader of the Liberal Democrats later.
The 74-year old is expected to be the only candidate on the ballot paper when nominations close at 16:00 BST.
Other possible contenders have all ruled themselves out, paving the way for the Twickenham MP and former business secretary to assume the leadership being vacated by Tim Farron.
Sir Vince, who has been acting and deputy leader in the past, has argued that Brexit is not inevitable.
Mr Farron stood down after a disappointing general election in which the party increased its number of MPs from nine to 12 but saw its vote share fall to 7.4%.
The party’s main campaign pledge during the election was to give the public the final say on the terms of the UK’s exit from the EU in a further referendum, ahead of the scheduled withdrawal date in March 2019.
Although Sir Vince has admitted this message did not “cut through”, he has argued that attitudes are beginning to change and that the public mood will come round to the party’s position.
He has said the Conservative and Labour leaderships are conspiring to negotiate a “hard Brexit” and he is willing to work with MPs from other parties to thwart this.
Sir Vince, who was knighted last year, is set to be elected unopposed after other potential candidates, including Jo Swinson, Norman Lamb and Sir Ed Davey, said they would not be putting themselves forward.
The veteran politician, who was a Labour councillor in the 1970s before defecting to the SDP and later joining the Liberal Democrats, has never stood for the party’s leadership before.
But he has become one of its most recognisable and influential figures, having served as deputy to former leaders Sir Menzies Campbell and Nick Clegg, and been a cabinet minister in the Tory-Lib Dem government for five years.
He will be the oldest leader of the party in its near 30-year history.
‘Energy and experience’
He has insisted he has the energy, as well as experience, to lead Lib Dems into the next election, which he believes will happen sooner rather than later.
Mr Farron announced his decision to quit a week after last month’s poll, citing the pressures of trying to reconcile his Christian beliefs with his leadership of a progressive political party.
He later revealed that he had decided to step down during the campaign, in which he was forced to clarify on several occasions his views on whether gay sex was a sin or not.