From the comments

…in 1981 Margaret Thatcher cut UK government spending in the middle of a recession, and against the advice of 391 economists that it would worsen the recession, and UK GDP started its recovery the same quarter. In 1991 Ruth Richardson in NZ cut government spending against the advice of 15 economists, and NZ GDP started its recovery the same quarter. There are a number of other cases of expansionary fiscal consolidations, and there's a causal theory to explain why this can happen – see http://ideas.repec.org/p/cpr/ceprdp/417.html (shortly, it's that cutting government spending improves people's expectations about the future of the economy and taxes, so they start investing more right now). Of course, correlation does not prove causation, and perhaps there is something about the EU countries now that is so different as to the cases I cite as to make those results no longer likely to hold, but Krugman writes as if he has forgotten entirely about the 1980s and 1990s.

That is by TracyW.  Later in the thread she refers us to this paper, on how "contractionary" fiscal policy can be expansionary, and vice versa.