If we take the Panelbase poll from September (which divided the Scottish electorate into four groups, Yes-Leave, Yes-Remain, No-Leave and No-Remain) and combine it with the findings from the recent YouGov poll that found that 15% of the voters who voted Yes in 2014 would now vote No and that 10% of former No voters have moved to Yes, we can draw an interesting graph.
I'm assuming that the two groups losing voters are Yes-Leave and No-Remain because they're both desperately unhappy with what's happening. So in the pie chart above I've split Yes-Leave into Yes-Leave-Yes (bluish yellow) and Yes-Leave-No (bright yellow), and No-Remain into No-Remain-No (green) and No-Remain-Yes (turquoise). Of the two groups changing their Indyref stance, Yes-Leave-No is slightly bigger than No-Remain-Yes (7% vs. 5%). This is consistent with the fact that YouGov found a tiny drop in the support for Yes.
So basically the polls are practically static because we're losing slightly more voters to No than we're converting to Yes.
We should be optimistic, however. We're unlikely to lose many more Yes-Leave-Yes voters to Yes-Leave-No – surely most of the remaining ones are so strongly pro-independence that nothing can convert them to No – and the Yes-Remain voters are unlikely to go anywhere so long as the Scottish Government remains pro-EU. At the same time, 24% of voters are still to be found in the No-Remain-No camp, and one would expect more of them to drift towards a Yes when it becomes a certainty that the UK is heading for a hard and messy Brexit with no special status for Scotland.
In other words, I expect the polls will start shifting towards Yes soon.