A wobbly left and a wary right could cut the Labour vote with low turnout | Robert Ford

Labour may currently have a commanding lead, but a second lacklustre half to the campaign could lead some voters to stay at home

Twenty-point poll leads, historic strength on all the polling indicators, a flailing opponent fighting for third place - and yet still Labour worries. It is no wonder.

Dark nights of disappointment in suburban leisure centres haunt Labour nightmares, with candidates and activists cruelly betrayed by late swings and polling errors: 1970, 1992, 2015 - every generation of Labourites bears its scars.