3rd May, And A Resignation Immediately Thereafter

No, not Blair, although no doubt he will. I mean that, unless the allegedly super-popular Cameron delivers truly enormous Tory gains outside the South East (where the Tories already hold most of the seats anyway, so who cares?), then his super-popularity will be exposed as the media froth that it is, his position will thus become untenable, and he will have no honourable or credible option except to resign.