Greg Mankiw worries that disagreement over fiscal stimulus will obscure the fact that economists agree about lots of things. There is economic consensus about public policy, and Mankiw reprints a nice table from his own textbook to prove it. But item # 4 on that table suggests that there isn't actually much disagreement over fiscal stimulus:

Fiscal policy (e.g., tax cut and/or government expenditure increase) has a significant stimulative impact on a less than fully employed economy. (90% [of economists agree])

Greg notes that this item doesn't distinguish between taxes and spending, which is fair enough. But many of the stimulus critics to which Mankiw has linked (e.g., Eugene Fama) don't distinguish between taxes and spending either. Mankiw's textbook says these economists are well outside the mainstream.