On current polling, the most important seats are the Labour held marginals, which aren't affected by this announcement.
a) We are a long way off that
b) By that point we are already in hung parliament territory
- Barrow and Furness
- Great Grimsby
- Workington
-Bridgend
- Gower
-Stoke-on-Trent Central
etc.
On the other hand, they may now feel more comfortable voting BP because they feel they can do so without blocking a Tory government.
Counterintuitively, this will therefore means the Tory lead in the polls will need to be LARGER in order to get a majority.