Have to see how this plays out in terms of what will probably be unpredictable splits and shifts, but on the face of it it's a disaster for Labour. I suspect Farage will get a bit of stick for this and there will be a tiny boost for ukip, but the bigger picture is messy but good for the tories. It's up to Labour to present this as a capitulation by johnson, a hard right alliance etc.
Lib Dems are already doing this, using image of Borias in Falange's pocket.