Smithson, of course, is just making his customary mistake of assuming that the SNP have some sort of decision to make on how to vote on a no confidence motion, and that the way they jump will be cynically determined by their own immediate electoral prospects. It's been pointed out to him umpteen times that it is utterly inconceivable for any left-of-centre party in Scotland to do anything other than vote to bring down a Tory government if the opportunity arises. But that message just isn't getting through to him, and I suspect it never will. Can you imagine what would actually happen if the SNP even abstained on a no confidence vote? It wouldn't just be a problem at the next election, it would haunt the party for decades to come. No, Mike, that was never an option, and it wouldn't have been an option even if the SNP were at 6% in the polls.
I'm fairly sure that Smithson and McDonnell are both equally wrong about the SNP's expectations for seat gains and losses in a snap election. The polling average at the moment suggests that the SNP's lead over Labour has increased since June 2017, so it's obviously nonsensical for McDonnell to suggest that the SNP are resigned to losing seats. But on the other hand, the increase in the lead is not so dramatic that it couldn't be reversed (and indeed more than reversed) if there were the kind of sudden shifts of public opinion during the course of an election campaign that we saw last year. There are a large number of ultra-marginal seats, some held by Labour, some held by the SNP, meaning that relatively small swings could make the difference between landslide and disaster. Nobody can possibly say which way it will go on the basis of current polls, or at least not with any confidence. If the SNP are optimistic about their prospects, I would suggest it's more likely to be because they feel they've cracked the problem of finding a winning campaign strategy. It may well be (and I'm just speculating) that the recent relentless focus on cancelling Brexit for the whole of the UK has been designed to make the SNP look like the only logical home for Remainers in a 2019 election - and Remainers, let's not forget, make up 62% of the Scottish electorate. They're in the majority even in Moray (albeit only just).