Greg Mankiw reports that the yield curve is steep, meaning that long-term interest rates have risen. In my view, this is perfectly rational, and it shows that the short-run effect of the fiscal stimulus is negative, as Jeff Sachs predicted.
This is all based on a Keynesian type of macro analysis. As we know, most of the stimulus spending does not take place until next year and beyond, so the short-run gains are puny. On the other hand, the big increase in the projected deficit creates the expectation of higher interest rates, which raises interest rates now. These higher interest rates serve to weaken the economy.
According to this standard analysis, the stimulus is going to hurt GDP now, when we could use the most help. Much of the spending will kick in a year or more from now, with multiplier effects following afterward, when the economy will need little, if any, stimulus.
This is the flaw with using spending rather than tax cuts as a stimulus. The lags are longer when you use spending.
[UPDATE] It is important not to confuse the outlook for economic activity with the effect of the stimulus. Even if the stimulus has a negative impact, the outlook for economic activity could be positive, and this could cause an upward-sloping yield curve. But I'm not sure that the outlook is necessarily positive. Bond investors could simply be taking the view that with or without a strong recovery in real output, the deficit spending is going to be monetized at some point, leading to inflation and higher interest rates.