In politics, the issue is to have candidates that can perform
A politician is a salesman that sells ideas and strive to meet up expectations. Voters look at the salesman. Is he a credible salesman? They listen to what that the salesman says and ponder about how likely the salesman is to deliver what he promises to deliver. They might like or dislike what is on offer. If they dislike what is on offer, they might go against it and if they like what is on offer they might even disregard their first impression about the salesman (or salewoman).
The Liberal Democrats had been all over the place and in the spate of a few years have had more leaders that there were General Elections. Correct me if I forget all the names. After Paddy Ashdown came Charles Kennedy, Sir Menzies Campbell, Vince Cable, Nick Clegg, Tim Farron, Sir Vince Cable, Jo Swinson, Baroness Sal Brighton, Sir Ed Davey, and Mark Pack? For the duration of one Parliament they were in power in coalition with the Conservatives under David Cameron.
The Liberal Democrats - with a few exceptions - defined themselves as pro-EU. After the 2016 Referendum, the made themselves one of the stumbling blocks in the quest for Brexit. They desperately pursued the possibility of a Second Referendum with the hope of keeping Britain in the European Union. When that failed to cristalize, they went for a General Election that they strongly believed would give them what they wanted but from the start the struggle to reach an agreement with other political forces to overcome party political differences. They divided the Remain Camp because they couldn't possibly reach an agreement with Jeremy Corbyn. The fact that several Labour MPs and several Conservative MPs decided to join them was not an incentive to reach such agreement. She went as a far as saying that she would go against Article 50 and de-facto keep Britain in the European Union despite the outcome of the 2016 Referendum on EU Membership. This last act signalled the beginning of the end for Jo Swinson's leadership. The British Electorate could possibly stomach the idea of a Second Referendum. They couldn't possibly support somebody that talked about getting rid of the Article 50 straight away.
The issue for Scottish voters - Jo Swinson was at the time a Scottish MP - was to decide between an SNP that openly stood for Remain and also for Scottish Independence and a Liberal Democrat MP that stood for Remain but against Scottish Independence. The political fate of Jo Swinson was sealed. She lost her seat and as a direct consequence of losing her seat she could not continue as Lib Dem leader.
Voters didn't like the saleswoman, didn't believe that the saleswoman could deliver what she was offering and many even didn't like what she was offering. In the process, every single Labour MP and every single Conservative MP that defected to Lib Dems lost their seats. Even the possibility of a hang Parliament eluded them.
The agony for both Lib Dems and Labour is self-evident. For Labour, as some Labour representatives have publicly stated, the aim is to restore public faith. The party is a divided as before. It is difficult to find a unity candidate. London set itself apart from the rest of the Labour movement when Labour voters outside London decided that the only possible choice was to support the Conservative Party.
To say that the Labour Party has a mountain to climb would be a historic understatement. As long as whoever replaces Jeremy Corbyn is seen as a representative of the Jeremy Corbyn lobby, the Labour Party will struggle to recover.
Now, all eyes look towards the 2020 May Elections and in particular towards the London Mayoral Election in which an opponent of Jeremy Corbyn - Sadiq Khan - is likely to win a second mandate. Given the absence of candidates visibly able to unseat Sadiq Khan, the London Mayoral Election could serve to unite a very divided Labour Party.
Do you see Sadiq Khan as potential Labour Party leader? Nobody mentions Andy Burnham - present Mayor of Greater Manchester. Former Member of Parliament and former Cabinet Minister and a likeable individual far detached from Jeremy Corbyn's leadership and one of the centre-left politicians born in Liverpool - a northerner. If the Labour Party has any hope of bringing back traditional labour voters into the fold, choosing a man from Liverpool with proven political record would not be a bad choice. Sadiq Kahn would appeal to London. Andy Burham would appeal to the country as a whole.
Whoever is chosen now as leader could end up being the leader of a party forever in opposition but if the struggle ends up being a war between London and the rest of the country the Labour Party will have to decide between being a political party for London or being a political party for Britain.