Columnist Paul Krugman, economist or partisan hack? The answer is pretty clear from
"Krugman vs. Krugman [1]," a pre-Thanksgiving feast of Krugman hypocrisy from the Washington Post's liberal columnist Ruth Marcus, who is wise to how Krugman is excoriating Bush, the GOP and even Barack Obama for daring to suggest that Social Security may need some fixing up. 
Marcus showed how Krugman was uttering cautious notes on Social Security's financial stability during the Clinton years:
"Somebody should introduce Paul Krugman to...Paul Krugman.
"[A] decade from now the population served by those programs [Social Security and Medicare [2]] will explode....Because of those facts, merely balancing the federal budget would be a deeply irresponsible policy - because that would leave us unprepared for the demographic deluge, with no alternative once it arrives except to raise taxes and slash benefits." (July 11, 2001 [3])
"Broadly speaking, the next administration....will face two big economic tests. One....is whether it can stick to a fiscal policy, including a policy toward Social Security, that prepares this country for the demographic deluge." (Nov. 12, 2000 [4])
"The reason Social Security is in trouble is that the system has a large 'hole' - basically a hidden debt - because previous generations of retirees were paid benefits out of the contributions of younger workers....a multitrillion-dollar debt that somebody has to pay." (Oct. 1, 2000 [5])
"[B]ecause the baby boomers' contributions were used to provide generous benefits to earlier generations, there isn't enough money in the system to pay the benefits promised to the boomers themselves." (June 21, 2000 [6])
Krugman responded (hat-tip Don Luskin [7]) with a defensive display [8]of pique.