Krugman of July 8, 2010:
the sensible thing [would be to] run deficits while the economy is depressed, then turn to budget-balancing once recovery is well in place
So, Krugman says: Don't worry about balancing the budget, we can balance the budget later. That's what he says on the 8th.
Krugman of 9 July 2010:
And by the winter of 2008-2009, it was obvious that this was the Big One — which, if the aftermath of previous major crises was any guide, would be followed by multiple years of high unemployment.
On the 9th, it is obvious to Krugman that we're not going to have the kind of recovery that will bring the budget into balance.
Krugman does not have the answer.