"Brad DeLong argues, there’s a very good case to be made"

1. Fiscal contraction reduces output in the short run; this immediately means that part of the initial gain in terms of a lower deficit is offset by reduced revenue and higher safety-net spending. These effects are especially large when you’re in a liquidity trap, so monetary policy can’t fight the fiscal contraction.

2. Reductions in short-run output and employment take a toll on long-run growth, too: capital investment is depressed, workers lose their skills, and so on. This in turn reduces future revenues.

3. Meanwhile, with real interest rates very low — actually negative on 5-year bonds — the cost of borrowing now in terms of future debt burden is also very low.

So there is no plausible argument on behalf of the claim that fiscal contraction expands output; there is, on the other hand, a very plausible argument to the effect that fiscal contraction doesn’t even help the fiscal situation.