Libdems often win by-elections because a) they get the protest vote from disaffected Tories, and lose it at the next GE, when voters return their own party. And (b) it's one seat, which the Libdems can afford to chuck everything at. Their resources are far more thinly spread at a GE. But it suits the likes of Maire and Jobbie to say it's all about Boris. Temporarily perhaps but it'll take dynamite to dislodge him and he's got two years to prove them wrong. On the other hand, he could be gone by next week!!