Things look pretty bad. So why keep campaigning?
The left needs to talk to people to gain strength, and the Bernie campaign gives an “excuse” to do that. Even if Bernie has a 0% chance, we can use his campaign as an opportunity to start conversations.
Everyone we convince to vote Bernie has taken a step towards the left. You will not have a better opportunity to talk about left-wing ideas for a long time, even if the context limits what you can say.
So canvass, phonebank and talk to friends and family to the last. The miniscule, but nonetheless real, chance of winning is just icing on the cake.