On a series of conference calls with reporters and bloggers, Jason Furman, Deputy Assistant to the President for Economic Policy, defended the series of tax breaks and infrastructure investments that make up the White House’s new jobs package as both a short-term way to boost the economy and draw contrast with a Republican platform stuck in the past, and a long-term way to create better modes for business investment in the future. But he still left nagging questions about the relative benefits of a policy which even some Democrats are wary of, and which economists have found dubious in recent days.

By now we know the three policies that the President is packaging together as a jobs agenda, united by Furman on the theme of investment. There’s a $50 billion dollar front-loaded transportation infrastructure investment, which includes a National Infrastructure Bank to encourage private dollars. There’s a permanent extension of the R&D tax credit (costing about $100 billion over ten years), instead of the year-by-year approach to research and development we have now, which causes confusion and some lapses. And there’s the acceleration of business write-offs for 100% of capital investments in 2010 (starting at today’s announcement) and 2011, which could encourage as much as $200 billion in purchases; over time, this would cost only $30 billion in 10 years and even less beyond that, as companies would essentially be taking the immediate write-off for what they would normally deduct as it depreciates over time.

These are all ideas supported by Democrats and Republicans in the past. It doesn’t make them particularly stimulative. Serious questions have been raised by economists, who say that these policies wouldn’t move the needle on unemployment much, wouldn’t stimulate the economy in the manner predicted, wouldn’t create extra demand which is the entire problem with the economy right now, and could be used (in the case of capital purchases) to put people out of work. Furman gamely tried to rebut these critiques.

Furman told a Bloomberg reporter that the economic team felt the bonus depreciation piece was high “bang-for-the-buck” because it accelerates tax credits so businesses get them up front. He explained that businesses who are having trouble getting credit could use the purchasing to acquire what amounts to a zero-interest loan from the government. But a Goldman Sachs analysis showed that such a measure may not stimulate much purchasing until the drop-dead date at the end of the credit, in the 4th quarter of 2011, hardly a near-term stimulative maneuver. When asked about this Furman didn’t accept the premise. “We think it’ll affect business investment right away… Businesses may move up their purchases from 2012 or 2013, but we don’t think anyone would delay their investments.” Furman insisted that this credit would create demand. “When US businesses are investing, they’re buying from other American businesses and hiring more workers to use those investments,” he said.

On the R&D tax credit, Furman didn’t fully explain why a policy that gets extended every year would somehow be stimulative when made permanent. He said that we now have the worst of all possible worlds, where we pay out on the tax credit but the uncertainty around it causes businesses to not actually use it to expand their R&D. With a permanent credit it can be manage more effectively. But Austan Goolsbee, a member of the Obama economic team, devoted much of his early economic work to proving that this type of policy doesn’t work in the manner intended:

Although there appears to be an abiding faith among policy makers that tax incentives can influence the investment decisions of firms and serve as a tool for stabilizing the economy, empirical evidence for the connection is weak. Econometric research has commonly found that tax policy and the cost of capital have little effect on real investment. Economic theory predicts that the marginal user cost of capital should be the primary determinant of investment demand but actual estimates of the price elasticity of nvestment … mostly lie between zero and -0.4… The evidence that investment is only modestly responsive to price has been one of the most robust findings of the empirical investment literature…

In addition to their large revenue costs, investment tax subsidies may give large, unintended rents to capital suppliers without increasing real investment until several years later because of the short-run asset price responses of capital goods. For policy makers interested in using tax policy to stimulate investment or, especially, to smooth business cycle fluctuations, the results are not promising.

I asked Furman about this, and he replied that Goolsbee was part of the team that worked on this policy. Of course, that doesn’t mean he agreed with all of it. Furman cited studies contrasting Goolsbee, saying that 80% of the benefit to the R&D tax credit goes directly to creating jobs, and that under the new policy, businesses would get rewarded for expanding their research.

Some economists, like Marshall Auerback, appreciate the Administration’s new attention to the economy. And I’ve said repeatedly that Democrats needed something to run on in November. But apparently some of them are profoundly uninterested in using even these middle-of-the-road policies. I reported earlier that Michael Bennet rejected the infrastructure part of the proposal unless it was “paid for through unused stimulus funds.” Furman responded to this that “others in the White House do congressional relations,” but that the entire infrastructure proposal is in fact paid for, through repealing tax breaks on the oil and gas industry. That kind of measure got 35 votes when Bernie Sanders proposed it this summer, and I don’t exactly see any more for it now.

Furman kept trying to stress that these were long-run policies, that they include necessary reforms (like removing uncertainty on the R&D tax credit, or consolidating programs and including the infrastructure bank), and that they are fully paid for and fiscally responsible. What he couldn’t quite answer is how these small-bore proposals would create the jobs necessary to climb out of this crisis. There the answers got more vague.

And here’s the bigger point. If Republicans and some Democrats will fight you on the policy regardless, why in the world would you try to bank-shot a policy to get X amount of votes, instead of proposing as a campaign document what the economy desperately needs? Isn’t the best way to stimulate investment through investment? Isn’t the best way to get businesses to hire by generating demand?