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Is there - as John McDonnell suggests - something going on in the political undergrowth? Jeremy Corbyn has been endorsed by the NME and by the perhaps not quite so young (or fashionable) readers of Kerrang, the glossy rock periodical.

With YouGov and Ipsos Mori suggesting Labour's vote could skim the 40% mark - though still behind the Conservatives - the Labour leader's supporters are upbeat going into the last week of the campaign.

A member of Labour's NEC is putting great faith in Britain's youth. He suggested I looked at local election results in places such as Oxford, where a 100% increase in 18 to 24-year-olds had led to a 14% swing to Labour. With nearly one million young people applying to vote since the election was called, he thinks a hung parliament is within reach.

But the website Election Data points out that most of the seats where young people outnumber the over-65s are already held by Labour, and it is sceptical of the prospects for further advancement.

Having spoken to those closely involved in selected Labour campaigns where the party is defending majorities of between 1,000 and 8,000 votes - and to some of those involved in the national campaign - the tone is rather more sober.

Most report there has been an increase in support amongst first-time voters but campaigners say that - despite more criticism of Theresa May since her social care scare - there is not much evidence of older voters switching to Labour in great numbers.

There are hopes that Labour will snatch some seats from the Conservatives - and one from the SNP - but the widespread expectation is that there will still be a net loss of seats on Thursday.

And - ironically - some say the only reason Labour's vote is holding up is because its candidates are running highly local campaigns which make no mention of Jeremy Corbyn.

So some Labour politicians are already turning their minds to what happens in the 24 hours after the result.

If Labour doesn't deprive Mrs May of her overall majority, what seems likely is that there will be a battle of the narratives on the airwaves.

There appears to be (in England) a return to two-party politics, with polls suggesting Labour would be in second place and the smaller parties would face a squeeze.

So pro and anti-Corbyn camps think it is likely that he will improve on Ed Miliband's share of the vote in 2015.

That may well encourage him to stay on in the short term - or indeed longer - even if Labour do not return to government.

His supporters are likely to rally under these circumstances, and those who want to oust him will face a difficult task.

So, the first priority of his internal opponents will be to get some traction for their narrative - that overall share of the vote matters less than either the total number of seats gained, or the gap between first and second place. And they will argue that Labour would have exploited Mrs May's difficulties better under different leadership.

Although at least two MPs have well-developed "shadow" leadership campaigns, these might not be activated unless, and until, that argument is won among the wider left-wing membership.

Those closer to Mr Corbyn would argue that he has re-energised Labour, brought in some people who were previously disaffected with politics and encouraged younger people to vote for the first time. All this provides a strong foundation on which to build for the future. If he goes, he should choose when the time is right, and that is certainly not now.

Of course if his supporters are right and something is going beneath the political radar which only a brace of pollsters have discerned, then in the 24 hours after the result, questions would be asked not about Jeremy Corbyn's future - but the prime minister's.