"However, you could cover your entire house in Labour posters, it won't make a difference. Labour have absolutely no chance at winning, won't even be close."
You see, this is why I think in this Election, if not others, putting up a Labour poster might actually help. Because we are repeatedly being told that there's no chance of Labour winning, not a hope, not under Corbyn, etc, etc. The media in particular is like a broken record on it.
It therefore becomes a self-fulffiling prophecy, and people who would like to vote Labour will start thinking they can't, because it's a wasted vote as they won't possibly win - and therefore they won't. So on this, occasion, seeing Labour posters around, whilst it won't change the vote of someone with a strong party allegiance may encourage a nervous potential Labour voter because they can see there's more support for the party out there then they've been told.
I don't know if Labour will win, tbh. I would like them to, but I have low expectations of the general public and even then they fail to live up to them, so it wouldn't surprise me if May wins. Sicken, dismay and distress me, yes, but not surprise me.