So then: the April Revolution is over. The LibDems vote seems soft, and they’re falling back. Most people who are going to vote Labour have now made their minds up (they’ll be slightly over a quarter of the electorate). The Undecideds remain – and yes, they are going to decide this – whatever Janet Daley thinks. Janet’s Torygraph piece was interesting, but wrong: she said the vast majority of Undecideds are ‘apolitical or antipolitical’,and in this she’s right. But the residue who aren’t will be absolutely decisive.

Lord Mandelson’s “two thirds still deciding” is at best half that; and on past performance, a good 70% of these will return to their normal ‘x’ box on entering the Booth. In short, around 1 in 10 will make up their minds in the next 36 hours, and they will do one of three things: vote Conservative, vote Libdem, or abstain. The vast majority of those still in this segment will not abstain. Thus, around 8% is still up for grabs. This is the remaining battleground.

When Ed Balls and Peter Hain start wittering about something, you can be sure it’s irrelevant – and their views on tactical voting are no exception. Tactical voting is hugely overrated by the media: voter responses are usually to prompted research questions, rather than spontaneously expressed intentions; and in reality, very few people are alive to the fact that they live in a marginal constituency. People will vote tactically to get rid of somebody they dislike (like Bercow) but on the whole it is rarely a factor – decisive or otherwise. People simply aren’t that interested.

So who are the Undecideds? And the short answer is,we don’t know. The media (as always) invent types – ‘Mondeo Man’ and similar cod psychography – but they don’t know either. What we can tell from past elections, however, is that they tend to be family-rearing women. And while again this is a bit of a generalisation, they tend to vote Conservative. So although Sky News leads this morning with ‘Tory vote static’ my response is, “Well it would be, because the Undecideds are still, um, undecided”.

The final factor is the weather. The Met Office is saying cloudy with rain. This tends to deter some older (and all ages of Labour) voters, but they’ve already lost anyway. Determined young mums vote in any weather.

So the Big One now is who youngish mums are likely to prefer: Nick Clegg or David Cameron. Gaffes could destroy this prediction, but my gut feeling is that Clegg peaked too early – and scrutiny of some of his policies has led exactly this type of undecided voter to question his competence. Plus Cammers is being seen to try very hard….and took the brave step of saying the LibDems could go whistle in the dark: he’d rule as a minority if necessary.

I think that has played well among the late-mindmakers. And therefore, my rule-of-thumb prediction is that the Tories will win by between 10 and 20 seats.