Is There a Sea Change in the Labour Party?

Labour have a well established poll lead over the Tories. But do those leads indicate to people actively voting for Labour now? Do you think they've moved it? There's a kind of sea change that happens when people are not just irritated with whoever's in power, but actively enthusiastic about you. For a lot of Labour MPs, it feels like this is the first time they really actually believe they could win - and I don't see them relaxing or throwing caution to wins.