Barack Obama doesn't want to own the economy. He's desperately anxious for voters to regard it as still belonging to George W. Bush.

This week, however, Obama made an aggressive attempt to own the economy as a political issue, making a series of new proposals and then daring Republicans to block them.

Obama proposed an additional $50 billion in infrastructure spending, a publicly sponsored infrastructure bank to leverage local government and private commitments, increasing and making permanent the corporate research and development credit, and allowing corporations to write off the full cost of capital expenses through 2011.

This adds to his small business bill pending before Congress, which temporarily excludes some investments in small business from capital gains taxation and establishes a $30 billion TARP-like fund for public investments in community banks.

According to Obama, these are mostly ideas similar to those Republicans have advocated. So, the only reason Republicans would oppose them is political obstructionism.

This is very odd politics. Obama is trying to put Republicans on the defensive for this November's election, an understandable political objective. But implicit in his formulation is that Republican approval, however suppressed, is an indication of sound economic policy. So Obama is unintentionally reinforcing a view detrimental to his cause that voters are increasingly coming to.

Still, Obama does have a point. Except for the additional stimulus spending, these are ideas Republicans have advocated or plausibly would advocate if in charge.

This, however, doesn't demonstrate their wisdom. Instead, it shows that Republicans share the Democrats' faulty instinct of using fiscal policy to try to manage the short-term performance of the economy.

Temporary spending or taxation measures are not without effect. They are simply without lasting effects and usually make long-term recovery more difficult.

The U.S. corporate income tax is a mess. A case can be made for allowing same-year expensing of capital investments rather than depreciating the assets over several years.

But doing so on a temporary basis, to the extent it has any effect, for the most part simply moves future investment forward a little.

And in this case, it will probably do very little of even that. The primary result of same-year expensing is to temporarily reduce corporate income taxes, thus increasing corporate cash. But American corporations are already awash in cash. That's not a current economic problem.

In a healthy economy, business decisions to buy equipment or hire more workers are based upon reasonable expectations that such spending will produce long-term returns. Government attempts to influence these decisions in the short-term can only result in unhealthy economic distortions.

This is not to say that government should remain idle in severe downturns such as this. Spending on income support programs to help people cope while the economy makes necessary corrections is a worthwhile countercyclical measure. That's why, so long as the ratio between job openings and job seekers remains so bleak, extending unemployment benefits is a sound decision.

The important economic differences between Democrats and Republicans are regarding long-term economic growth strategies. Democrats believe long-term growth is driven by government spending and government allocation of capital. Republicans believe government, rather than driving economic growth, is dependent on the success of private investment.

That's the heart of the dispute between the parties over increasing income tax rates on the affluent. Democrats believe the money will be used more productively by government. Republicans believe siphoning off an important source of private investment is a serious mistake.

Both parties, however, believe in the conceit that a $14 trillion dollar economy can be managed quarter-to-quarter from Washington D.C.

In the short-run, fiscal and monetary policy can wreck an economy. But it cannot build or repair one. That takes time and a solid long-term foundation.