Acting Liberal Democrat leader Sir Ed Davey has launched his bid to lead the party permanently with a vow to improve conditions for carers.
The Kingston and Surbiton MP has been serving as interim leader since Jo Swinson stepped down after poor results in the 2019 election.
He joins Layla Moran and Wera Hobhouse in the race for the top job.
The contest, initially delayed until May 2021 due to coronavirus, will now take place this summer.
Candidate nominations will be open from 24 June to 9 July, with the ballot running from 30 July to 26 August, after which the winner will announced.
The party plans to run virtual hustings events with candidates, with its annual conference also due to take place online towards the end of September.
Sir Ed, a former energy secretary in the Conservative-Lib Dem coalition, unsuccessfully stood in the party's 2019 leadership contest won by Ms Swinson.
Launching his campaign this time round, he said the party should focus on creating a "liberal, greener and more caring society".
He said the experience of acting as a carer for his disabled son had shown him that "far too often carers get a raw deal".
"A caring revolution starts by properly recognising the unpaid work so many do looking after loved ones - and a citizens' basic income could do just that," he said.
Internal election review
In an interview with the Guardian, he said he also wanted to recover the party's reputation as "champions on education and the environment".
Suggesting the party needed to outline a broader policy agenda beyond Brexit, he added: "you can't define a party by an issue which will go, which is transitional".
It comes after an internal inquiry last month likened the party's 2019 election campaign, at which it returned just 11 MPs, to a "high-speed car crash".
The report found the plan to stop Brexit without a second referendum was used against the Lib Dems and called "undemocratic" by other parties.
Runners and riders
"Beyond 'stopping Brexit', our other policies and messages struggled to cut through," the report said.
Oxford West and Abingdon MP Layla Moran, currently the party's education spokesperson, declared her intention to run for leader in March.
Bath MP Wera Hobhouse announced she was entering the race in February.
But St Albans MP Daisy Cooper, who had also been tipped as a contender, joined Christine Jardine in ruling herself out of the contest last month.