David Leonhardt has emerged as one of the most able defenders of the Obama economic policy agenda. The trouble is that doing this job well sometimes means doing the job of educating the public about the evidence at hand slightly less well.

In his latest column, Leonhardt offers a very robust defense of the federal stimulus program, but it doesn’t seriously engage with criticisms of the program, apart from a stray Herbert Hoover joke.

The case against the stimulus revolves around the idea that the economy would be no worse off without it. As a Wall Street Journal opinion piece put it last year, “The resilience of the private sector following the fall 2008 panic — not the fiscal stimulus program — deserves the lion’s share of the credit for the impressive growth improvement.” In a touch of unintended irony, two of article’s three authors were listed as working at a research institution named for Herbert Hoover. [Emphasis added.]

While I’m sure that some critics of ARRA believe that “the economy would be no worse off without it,” this view doesn’t even apply to the op-ed by Cogan, Taylor, and Wieland. The authors suggest that increased transfers were saved rather than consumed, and that the modest increase in government spending did not make much of a contribution to growth relative to the resilience of the private sector. Even the architects of ARRA acknowledge that the government spending piece was being rolled out over a longer period of time. Cogan, Taylor, and Wieland were making a very narrow point regarding the effectiveness of the stimulus up to September of 2009. For Leonhard to use this as his foil is thus a bit of a stretch. One assumes that Cogan, Taylor, and Wieland would offer a different analysis of the impact of ARRA through the present, if only because there has been more time for government spending to trickle through the economy. This begs the question, of course, of whether there were better, faster-acting alternatives that could have stemmed the sharp spike in unemployment. But again, apart from the laugh line about Herbert Hoover, it’s not clear what citing this op-ed really accomplishes for Leonhardt.

Leonhardt refers to “hard-core skeptics,” and my worry is that this does a lot of the work for him. Critics like Desmond Lachman believe that the stimulus was poorly timed and poorly designed. This suggests that he is not a hard-core skeptic, though of course many if not most skeptics and critics of ARRA fall into this camp. Others are concerned about the impact of heavy deficit spending on long-term growth prospects, i.e., the fiscal stimulus program has a beneficial growth impact in the short term, but exacerbating extreme fiscal policy swings are very difficult to sustain. These critics are also not hard-core skeptics. So is Leonhardt taking issue with people who believe that spending hundreds of billions of dollars in the space of a few month would have zero impact on GDP growth? In that case, I would enthusiastically agree with him.

To bolster his case, Leonhardt cites Reinhart and Rogoff. The trouble is, he never acknowledges one of their central findings.

Around the world over the last century, the typical financial crisis caused the jobless rate to rise for almost five years, according to work by the economists Carmen Reinhart and Kenneth Rogoff. On that timeline, our rate would still be rising in early 2012. Even that may be optimistic, given that the recent crisis was so bad. As Ben Bernanke, Henry Paulson (Republicans both) and many others warned in 2008, this recession had the potential to become a depression.

Yet the jobless rate is now expected to begin falling consistently by the end of this year.

This is very interesting and important. Of course, Reinhart and Rogoff have made another important argument, which the WSJ’s excellent Real Time Economics blog made note of early last month.

In a new paper presented Monday at the annual meeting of the American Economic Association, Carmen Reinhart of the University of Maryland and Kenneth Rogoff of Harvard study the link between different levels of debt and countries’ economic growth over the last two centuries. One finding: Countries with a gross public debt debt exceeding about 90% of annual economic output tended to grow a lot more slowly. For advanced countries above the 90% threshold, average annual growth was about two percentage points lower than for countries with public debt of less than 30% of GDP.

The results are particularly relevant at a time when debt levels in the U.S. and other countries at the center of the financial crisis are rapidly approaching the 90% threshold. Gross government debt in the U.S., for example, stood at 85% of GDP in 2009 and will reach 108% of GDP by 2014, according to IMF projections. The U.K.’s gross government debt stood at 69% of GDP in 2009 and is expected to reach 98% of GDP by 2013.

“If history is any guide,” the rising government debt “is very troubling for the U.S. and other advanced economies,” says Ms. Reinhart. [Emphasis added.]

Surely this is worth noting in a column on the likely impact of a debt-financed fiscal stimulus program. If Leonhardt intends to knock down a straw-man argument — ARRA has had no impact and the economy would be in the same shape without any fiscal stimulus program — he succeeds. But of course economists like Michael Boskin, who is also affiliated with Hoover, argued that there were cheaper alternatives that would yield better overall employment outcomes. Boskin could be wrong. Yet his argument is one that deserves to be taken seriously. Note that Boskin’s argument does not “revolve around the idea that the economy would be no worse off without” the stimulus. Rather, he suggests that it had less impact than the business cycle, the Fed’s zero interest rate policy, and the automatic stabilizers in the tax code. That there is an important different between this argument and the argument that the economy would be no worse off without the stimulus should be obvious.

As Jeffrey Sachs — an economist at Columbia University’s Earth Institute, which is not named after Herbert Hoover — has argued, the U.S. has engaged in extreme policy swings on the fiscal and monetary side for much of the last two decades, and the consequences have been dire. There is a value in crafting sustainable policies that might not have the same short-term impact, but that are likely to yield better outcomes over the long term.

Rather than make any reference to the fact that impact of massive fiscal deficits on long-term growth, Leonhardt cites the following:

For that, the stimulus package, flaws and all, deserves a big heaping of credit. “It prevented things from getting much worse than they otherwise would have been,” Nariman Behravesh, Global Insight’s chief economist, says. “I think everyone would have to acknowledge that’s a good thing.”

But again, I don’t thing that anyone doubts that ARRA helped perk up growth. It is very hard to imagine that spending an enormous sum of money would not. One wonders: does Nariman Behravesh believe that ARRA was the best use of $862 billion (the actual cost of ARRA according to the best recent estimates) relative to plausible alternative proposals? Perhaps he does. This strikes me as a question worth asking.

I can see why many journalists who see members of the Obama administration as smart, reasonable people are eager to defend them. I see them as smart, reasonable people as well. I think that I’m helping them do their job well by faithfully representing critical views of their policies to the best of my ability.