Ideological campaigning is all they've got left: they've failed across the board to make any other case. Economically we're now being told from multiple academic sources that we'll be worse off. With regards to Europe several sources in the EU are telling us that Scotland's entry won't be automatic, that adoption of the Euro will probably be mandatory (and the UK Government is unwilling to say a Sterling zone is a possibility). Militarily our defence industry (Clyde shipyards specifically) would collapse and the plans for setting up the SDF are a shambles.
Pretty much every "real world" line of reasoning points straight back to the UK. The only reason the Scots will vote Yes now is because they either refuse to believe the tidal wave of unassailable refutations of the SNPs dreams or because they decide they don't care about the pain and that they hate the English.