Following the council and European Parliamentary elections, the Lib Dems were tipped to put forward a strong campaign. However, the party suffered a poor election and ended with 11 seats, one less than they had in 2017.
Speaking to Express.co.uk, Dominic Walsh, policy analyst for think-tank, Open Europe, said as soon as Boris Johnson managed to bring back his Brexit deal, the Lib Dems’ policy on revoking Article 50 effectively ended their campaign.
He said: “The revoke policy was a major unforced error, which may have undermined their argument that they were the moderate option in the election.
“It was one thing to call for revoke in an emergency to stop no deal, but once Johnson got a deal it looked like a much more extreme policy.”
Ms Swinson lost her seat of East Dunbartonshire to SNP candidate Amy Callaghan by 149 votes.
Under the party’s policy, a leadership election is automatically triggered if the leader loses their seat.
Sir Ed Davey has been tipped as the favourite to take over from Ms Swinson and become the party’s new leader.
Sir Ed admitted his party’s policy to revoke Article 50 was “not realistic”.
Although the party gained MPs from Labour and the Conservatives over its opposition to Brexit, every defector lost their seat.
The Kingston and Surbiton MP, is currently serving as the co-leader with party President, Sal Brinton until the new leader is elected.
Away from his party’s Brexit policy, Sir Ed also explained that Jeremy Corbyn’s unpopularity had cost the party.
Sir Ed said: “If there’s another Corbyn, we’re going to have to work out how to do well when the Tories and the Tory media are scaring everyone rigid about the impact of a left-wing Labour leader.
“If it had been a Tony Blair, Sir Keir Starmer if you like, what do we think the result would have been?
“It would have been very different.
Mr Corbyn has announced he will step down as leader from the party in March.
In the wake of the party’s worst election defeat since 1935, former MP Gloria De Piero hit out at the party and described their current predicament as a “car crash”.
Ms De Piero said: “The Labour Party is in a bit of a car crash at the moment and there will be a leadership contest.
“What is really, really important that this is not a beauty contest.
“We ask the right questions, who is the answer to the problems the Labour Party faces?”