> Thus, if you were a party who wanted to promise cutting taxes to the population you could, but you'd have very little impact on the taxation's bottom line.

Are we talking about the UK parliament cutting taxes, or the Scottish parliament? I get the impression that the article is talking about the UK parliament: the author is trying to explain why the Conservatives have limited support in Scotland, and why they're trying to make the Scottish parliament responsible for raising their own taxes.

But if the UK parliament cuts taxes everywhere (including Scotland), and that has little effect on Scottish spending, then it seems like incentives are such that the Scottish population would most likely support that.

OTOH if it has disproportionate effect on Scottish spending, they would oppose. But if I read you correctly (do I?), you're saying that's not true; and a priori I have no particular reason to expect that the effect would be small or large relative to the cut.