The case seems pretty overwhelming:
"When the U.S. government can borrow at a real interest rate of -0.65%/year for five years, the case for larger deficits now--for pulling spending forward from the future into the present and pushing taxes back from the present into the future--is unanswerable: of course the government should borrow more on such terms: households value the taxes they will pay in the future if taxes are pushed back as much less painful than the taxes they would otherwise pay today, and a huge number of government spending programs offer at least a zero percent real rate of return via their effect on the productive capacity of the economy. Even if expansionary fiscal policy had no effect on capacity utilization and unemployment bigger deficits now while the government can borrow on such terms would be a no-brainer. And since expansionary fiscal policy does have such effects, it is something that you should advocate even if you have less than no brain at all--even if you have a negative brain."
Worth looking at Meltzer's arguments against more expansion and Delong's response