Could the Lib Dems win even fewer seats next year?

I was asked by The National yesterday for an opinion on how many seats the Liberal Democrats are likely to win at the Holyrood election next year.  I don't think what I said has made it into the paper, so I thought I'd briefly explore the point here, because it's an intriguing one.  The Poll of Polls last weekend had the party on exactly 6% on both ballots - meaning that in comparison to the 2011 result they're up a trivial amount on the list, and down just a couple of points in the constituencies.  So essentially nothing much has changed, and on the face of it they should be on course to at least hold their five current seats.  But the complicating factor is that nobody knows what impact the Alistair Carmichael affair has had on Lib Dem support in their traditional fortress of the Northern Isles, which provides them with a full 40% of their current representation.  It's not impossible that their iron grip on the Shetland and Orkney constituencies could be loosened this time around.

If they did lose either or both of those constituency seats, could they make up for it on the list?  This was the list result in the Highlands & Islands region in 2011 -

SNP 47.5%
Labour 14.5%
Liberal Democrats 12.1%
Conservatives 11.6%
Greens 5.1%

Of the eight constituency seats, the SNP took six, and the Lib Dems took the other two.  The SNP claimed an additional three seats on the list, while Labour and the Tories took two list seats each.  So superficially it might look as if the Lib Dems were safe enough - ie. they would have ended up with two seats in the region anyway, regardless of whether they had won the Northern Isles constituencies.  But of course the snag is that a significant minority of their list votes in the Highlands also came from Shetland and Orkney.  If they take a hit on the constituency ballot in the Northern Isles next year, it's highly likely that they'll take a hit on the list vote there as well - and any sort of slippage at all will render them highly vulnerable to losing one of their two seats in the region.  On the 2011 result, a 2% drop would cost them a seat, but in reality even a smaller drop than that would leave them requiring a lot of luck - they'd be relying on the Tory and Green votes not increasing very much.   Even the SNP could conceivably snatch the seat with an extra few points of support. (I'm excluding the possibility of a Labour increase, because that's probably less likely, but you never know!)

The counter-argument is that the Lib Dems could compensate for a declining list vote in the Northern Isles by growing their support in the rest of the Highlands & Islands region, and doubtless their more optimistic activists would point to a recent local by-election result as evidence that a recovery is underway in that part of the world.  But one swallow doesn't make a summer, and all that.  My own view is that the loss of either Shetland or Orkney would probably leave the Lib Dems with even fewer MSPs across Scotland than they managed to cling onto after their calamitous campaign four years ago.