It's a brave man who uses a headline like that given the accuracy of Silver's predictions in last year's US presidential contest, but nevertheless I am going to confidently take issue with his claims reported in the Scotsman that the Yes side have "almost no chance" in the independence referendum. The main reason is that there are ample signs that his opinion is based on a fairly cursory look at the polling data - by contrast he would never put his neck on the line with a US political prediction without being totally immersed in every available statistic and variable.
1) He claims that the polling evidence is "pretty definitive" in putting the Yes side at 40% (give him his due here, he's at least not making the all-too-common schoolboy error of assuming that Don't Knows can be lumped in with Nos). But this ignores the Panelbase polls, which inconveniently and consistently diverge from the "definitive" pattern. Is Silver even aware of those polls? We don't know, but we do know that Panelbase is a credible polling company that adheres to British Polling Council rules, and we also know that no less a figure than Professor John Curtice has cautioned that for as long as one polling company is diverging from the others, it would be wrong not to at least consider the possibility that they are getting it right and that the others are getting it wrong.
2) He claims that the "No side is even more dominant with younger voters, so there's not going to be any generational thing going on". That's an utterly extraordinary claim given the number of polls - and not just Panelbase polls this time - that have suggested the complete opposite is true. For example, an Ipsos-Mori poll earlier this year showed that no fewer than 58% of 18-24 year olds were planning to vote Yes. Is Silver even aware of polls like that? Or did he just look at the MRUK youth poll that was so widely reported by our impeccably neutral media, and assume that must represent the "definitive" picture?
As Marcia has pointed out in the comments section at Wings, a further problem with Silver's remarks is one that is not specific to Scotland - namely the idea that No campaigns usually gain ground rather than lose it in referendums. (Again, to be fair, he at least doesn't make a prize idiot of himself in the way that Peter Kellner did by pretending that this represents some kind of unbreakable "iron law".) Matt Qvortrup made a similar grandiose claim recently, before backtracking somewhat on Twitter and conceding that the Yes campaign in the Montenegrin independence referendum did indeed gain ground as the campaign progressed - which they needed to do, because they looked likely to fall short of the artificial 55% threshold. But as Marcia has noted, a much better example is the monumental gains that the Yes campaign made over the course of the 1995 Quebec independence referendum campaign. Qvortrup apparently thinks that he can completely dismiss that example because Yes ultimately still lost by a whisker, but that's incredibly woolly thinking from an academic. The salient point is that huge numbers of Quebec voters who initially told pollsters they were planning to vote against independence ultimately walked into a polling station and voted in favour of it - and moreover they did so knowing that there was a severe "risk" that their votes could swing the balance. It was no protest vote.
That was something that simply shouldn't have happened if you believe Silver, Qvortrup and Kellner - so why did it? My guess is that, paradoxically, the more important a referendum is, the less likely voters are to swing to No by default. The supposed tendency that Silver talks about is largely a side-effect of electorates so often being faced with relatively trivial matters in plebiscites. Take the AV referendum, for example - the prevailing attitude among the public seemed to be "I don't give a monkey's about this, it's irritating to even have to think about it, so unless someone can give me a very good reason I'll just vote to keep what we already have". That kind of lazy thinking clearly went out of the window for Quebec voters when they were faced with the most important choice of their lives, and I'm confident it will go out of the window for Scottish voters next year. We will be dealing with an electorate that is engaged like never before - and as recent research has shown, the better informed that voters consider themselves to be, the more likely they are to vote Yes.