The Tories are clearly sensing victory in Norwich North, David Cameron and George Osborne will both travel up there and be canvassing tomorrow morning from 5.30am. The Tories think that a victory would send them into the summer with the momentum and show that they are the party in poll position after the whole expenses business. Certainly, a win—and we’ll know if they have done this by around noon on Friday—would get the Tories some positive press coverage. But I suspect that a Labour defeat / Tory victory is already priced in politically.
The story to watch might actually be the performance of the Lib Dems. The word from Norwich is that they are really struggling and could be pushed hard for third by the Greens. Coming fourth in a by-election, traditionally a Lib Dem strength, would hardly be the start to the summer that Nick Clegg would want.