They could do worse than elect the young, dynamic LibDem, Luisa Porritt.
And a lot better too...
I admit she's not as bad as Siobhan Benita, who had been due to be the LibDem candidate for Mayor until the election was delayed; I met the latter when she stood as an independent mayoral candidate back in 2012 (she came to promote herself at a meeting I was involved in), and she was
seriously unimpressive (at least for any positive reasons). I don't have direct experience of Luisa Porritt, but I live in Camden (where she's a councillor) - and follow local issues quite closely - and I haven't noticed either her or the Camden LibDems arouse my interest lately...
Putting together considerations of policy and competence, I have no enthuisasm for any of the 3 main party candidates for London Mayor. (The Green Party one on the other hand... is a bit more sensible.) If I wasn't already ill-disposed towards the Tory candidate, his ill-informed remarks about the Met's Watford Extension [actually, diversion of course, not extension...], as reported here, would have done for him anyway.