Ukip is expected to elect its first female leader at the party’s annual conference, ahead of a struggle for relevance after the Brexit vote and departure of Nigel Farage.
The party is likely to see reduced numbers at the conference on Friday, as insiders confirmed that it was losing support to the Conservatives.
In a sign of the party’s problems, the former Ukip executive director Steve Stanbury said he was rejoining the Tories because “the party’s over, mission accomplished”.
Diane James, a former parliamentary candidate who came close to taking Eastleigh off the Liberal Democrats in 2013, is the strong favourite to win the leadership out of a wide field of relative unknowns.
If she succeeds, James will have to contend with a party riven by infighting between various factions, including Farage loyalists, a circle around the former Conservative cabinet minister Neil Hamilton, and others close to Douglas Carswell, the party’s only MP.
Several Ukip sources said James had the tacit backing of Farage, after party authorities excluded Steven Woolfe, the Ukip immigration spokesman, from running, because he submitted his papers 17 minutes late.
Many of Woolfe’s backers, including the donor Arron Banks, have transferred their support to James in the hope that she will try to reform the party’s structures.
In an interview this summer, James indicated that she would take a tough line against plotters, saying: “There’s going to be no place in Ukip under my leadership for those who have sought or seek to destabilise, destroy or even obstruct what a new constitution will outline for the new governance of this party.”
The other leading candidate, Lisa Duffy, a party organiser, has the support of the former deputy leader Suzanne Evans and Patrick O’Flynn, the MEP and former communications director, who have clashed with Farage since the 2015 general election.
The others in the race are the MEPs Bill Etheridge and Jonathan Arnott, Elizabeth Jones, the deputy chair of the Lambeth branch, and the former parliamentary candidate Philip Broughton.
There remains persistent speculation that Farage could make an attempt to return as leader in the coming months or years. He stepped down after the EU referendum, saying he had done his bit for the party. But rather than take a backseat, Farage has repeatedly resurfaced in recent weeks to intervene on Brexit.
He will give a keynote speech at the conference in Bournemouth before the new Ukip leader is announced.