I've just noticed an extraordinary New Statesman article from a couple of days ago, in which Stephen Bush reveals that extensive discussions with insiders have left him "more convinced than ever" that the polls are right, and that Jeremy Corbyn will become Labour leader in September. We should probably take that assessment seriously, as Bush wasn't wise after the event in respect of the general election - he warned before May 7th that the polls might be misleading, in which case the most likely outcome was a Tory-led government (albeit he thought the coalition with the Lib Dems would have to be renewed). My only quibble in this case is that the current polls aren't actually showing that Corbyn is the nailed-on winner - he has an enormous lead on first preferences, but all that matters is whether he is still ahead in the final run-off, and on that measure his lead is wafer-thin. Assuming the private poll we saw last night was legitimate, that should actually be regarded as a statistical tie between Corbyn and Yvette Cooper.
However, if Bush is correct that the polls aren't wildly inaccurate, it's clearly the case that Corbyn at least has an excellent chance. If he wins, it will turn the political world upside down, and the SNP will be affected just like everyone else. Here are a few potential implications -
1) Left-wingers who turned to the independence movement because the Britain of Attlee, Bevan and Benn seemed to be gone forever may start to have second thoughts. I know the counter-argument is that it will shortly be demonstrated that Corbyn is unelectable in the south, but in truth I wouldn't be at all surprised if he enjoys a prolonged honeymoon period in the polls. Even Michael Foot enjoyed a poll lead over Mrs Thatcher at times. If that happens, it will fuel a (possibly misplaced) sense in the Scottish left that all is not lost at UK level after all.
2) The SNP will, without changing any of their own policies, sometimes find themselves criticising Labour "from the right" for the first time in decades. Corbyn will probably propose some nationalisations that the SNP think are a step too far, and he may also be more radical on taxation. Unless Corbyn compromises with the mainstream Labour view on defence and foreign affairs, the SNP may end up defending NATO against a Labour party that wants Britain to withdraw from the alliance. Speaking personally, I would find that incredibly disorientating, although admittedly it's a less important issue than Trident, on which Labour and the SNP would suddenly be on exactly the same page.
3) We won't have to worry any more about tactical unionist voting (or at least not to any great extent) - the choice between Labour and the Tories will become more polarised than at any time since the 1980s, and supporters of each side won't be lending each other votes to stop the SNP. In some cases, Tory voters may even revert to seeing the SNP as a legitimate 'moderate' tactical option for thwarting Labour. Admittedly, though, tactical voting was never really likely to be a major factor in the Holyrood election.
4) The SNP might find it harder to retain their overall majority next year. The "good" news is that politics is very personality-driven these days, and I suspect voters will still look at the choice between Sturgeon and Dugdale and conclude that it's a no-brainer. But the Corbyn factor could chip away at the working-class vote that defected to the SNP en masse in May, allowing Labour to lose less badly than they otherwise would have done. That could make all the difference if the SNP are seeking a mandate for an independence referendum (regardless of whether the proposal is conditional on Brexit or not).
Of course, all of this assumes that the Labour parliamentary party would accept a Corbyn win, which they may well not do. If there's a major breakaway, the SNP could end up being helped rather than harmed. It would be fascinating to see which way the Labour group at Holyrood would jump if they had to choose between two rival parties.