Ben Duncan has been blogging about the events leading up to Cllr Lainchbury's resignation, and Brighton Blogger Neil Harding has calculated a relatively small 3.5% swing needed if Greens are to win this seat.
We selected local resident Alex Phillips as our candidate for a Goldsmid by-election some weeks ago:

Alex is an excellent candidate, and will make a hard-working, dedicated councillor for Goldsmid ward should she be elected.
The question is, when will the Tories call the by-election? They won't want polling day to fall within the school holidays, so my guess is we'll hear something next week - and then it will be back into the fray.
A Green win in Goldsmid would put us on an equal footing with Labour, with 13 seats apiece, and the Tories would no longer have a workable majority at the council, even with the support of the one independent (former Tory) councillor.
As Ben says, interesting times...