Finally the election explodes into life as YouGov poll moves the race closer to hung parliament territory

Whenever you see a Britain-wide poll showing a huge Tory lead (which has basically been every single poll in this campaign so far), it's worth bearing in mind that Jeremy Corbyn's theoretical objective is not to overturn that lead, but simply to bring it down to a level that might conceivably translate into a hung parliament rather than an overall Tory majority.  That's still a mind-bogglingly tough hurdle for him, but it does put a slightly different perspective on things, because depending on the distribution of votes even a 6 or 7 point Tory lead might not be quite enough for a majority.

Earlier today there were two polls which showed modest declines in the Tory lead, but which still left Theresa May with a very comfortable 12 or 13 point cushion.  However, both of those polls were largely conducted before people became acquainted with the controversial Tory manifesto, and the million dollar question was what impact that would have.  Expectations genuinely differed - some commentators thought working-class voters would be taken in by the faux 'redistributive' aspects of the manifesto, while others thought the Tories were taking a big risk with their core vote.  Judging by the newly-released post-manifesto poll from YouGov, the latter analysis may have been closer to the mark.

GB-wide voting intentions (YouGov) :

Conservatives 44% (-1)
Labour 35% (+3)
Liberal Democrats 9% (+1)

SNP / Plaid Cymru 5% (n/c)
UKIP 3% (-3)

For the first time in the campaign, then, we have a poll that makes it look just about plausible that we could end up with a hung parliament - the Tory lead would only have to slip two or three points more.  I still think that's highly unlikely - if anything, it's more probable that this is just a blip and the gap will widen again as polling day approaches.  But it's certainly electric shock treatment for a campaign that until now has been the dullest since at least 2001.

For reasons only they can explain, YouGov never reveal the SNP's vote share until the following morning, but judging from the percentage changes of the other parties there's no obvious reason to suppose the SNP have slipped back.  [Update : The SNP and Plaid are unchanged on 5%, and the SNP lead the Tories in the Scottish subsample by 44% to 28%.]

UPDATE : Hot on the heels of YouGov comes a post-manifesto Survation poll which goes some way towards confirming that there has been a telling swing from Tory to Labour, but which still leaves Corbyn with a bigger deficit than he has in the YouGov poll.

GB-wide voting intentions (Survation) :

Conservatives 46%
Labour 34%
Liberal Democrats 8%
SNP 4%
UKIP 3%

A more realistic hope than a hung parliament is that the Tory surge we saw at the start of the campaign may have now gone into reverse, and that we'll see the effects of that in Scotland as well as south of the border.  If so, the SNP lead over the Tories might just start to inch up, and some of the Tories' longer-shot constituency targets might begin to look out of reach.

UPDATE II : I've removed the percentage changes from the Survation numbers above, because they were comparing apples with oranges - this is an online poll, and Survation's other recent polls (for Good Morning Britain) have been conducted by telephone.