It’s not that he doesn’t occasionally make decent points. It’s that he’s so interested in scoring some disingenuous rhetorical blow that he fails to think much about what he’s writing, or its implications. For instance, he has questions he’d like to ask the president:

1. During your campaign, you said that under your tax plan, “no one will pay higher tax rates than they paid in the 1990s.” The House healthcare reform bill, however, raises tax rates for top earners well above the 1990s levels. In many states, the top marginal tax rate would exceed 50 percent. Do you still stand by that campaign pledge, and would you veto any bill that violates it?

2. During your campaign, you said, “The danger in a cap-and-trade system is that the permits to emit greenhouse gases are given away for free as opposed to priced at auction. One of the mistakes the Europeans made in setting up a cap-and-trade system was to give too many of those permits away.” The climate change bill now being considered in Congress does the same thing. Are you now willing to have the United States make the same mistake the Europeans made, or would you veto the bill?

Several things to note. First, that top marginal tax rate will apply to households earning over $1 million per year. I’d love to see Greg Mankiw really wrestle with the economic implications of raising that rate, as Tyler Cowen does, rather than just falling back on the baseline economic predictions. But Mankiw doesn’t do much wrestling on his blog.

Second, the next question is entirely aimed at gotcha points, since anyone familiar with the issue can tell you that: a) the original distribution of permits is irrelevant to the efficiency of the final distribution of permits or the actual reduction of carbon, which are functions of the cap and the trading mechanism, and b) Europe’s failure wasn’t about giving the permits away free, it was about having too many permits in the first place. I don’t know if Mankiw understands that the question he’s posing is nonsensical or not, but neither interpretation shines particularly well on him.

Moreover, Mankiw shows no particular interest in the actual policy at issue, or willingness to grapple with the question of second-best solutions, or recognition that policies basically never embody the theoretical ideal underlying them. He obviously understands how the sausage gets made, since he once helped make it, but on his blog he plays the political naif. You’d have to be completely ignorant of the issue to think that the Pigovian ideal would become law. Mankiw’s positioning on the climate change issue seems to indicate that anything other than a “perfect” cap-and-trade bill is veto worthy. This suggests that either he doesn’t actually care about climate change, or he does care but is willing to set aside that concern to score points by noting that the president isn’t generating the perfect economic policy. Again, neither interpretation shines particularly well on him.

Basically, Greg Mankiw is just about the least interesting economics blogger out there. I always know where he’s going to come down on an issue, and I never learn anything from his explanations of why he winds up at that position. He seems to care more about getting it Republican than getting it right, which makes for lousy econoblogging.