When the economic road gets bumpy, politicians of all stripes clamor to take the wheel. Some want tax cuts, some want a huge spending program, while others worry about ballooning the deficit.

James Bullard, president of the Federal Reserve Bank of St. Louis, has the same answer for all of them: Leave the driving to us.

In a new paper titled "Death of a Theory," Bullard argues that fiscal fine-tuning doesn't work. He sketches out a conventional wisdom that, he says, was widely accepted among academic economists before the recent recession.

That view held that the political system, because of all the delays involved in building consensus, passing laws and letting government contracts, is ill-equipped to respond to short-term economic challenges. Monetary policy is nimbler -- the Federal Reserve can cut interest rates immediately if it needs to -- so it was the preferred tool for stabilizing the economy.

The financial crisis put a chink in this argument. Once the Fed had cut rates to zero, some New Keynesian theorists argued, it was out of ammunition. A classic dose of fiscal medicine -- higher government spending -- was the only way to stimulate the economy.

Now, Bullard is pronouncing that brand of New Keynesian theory dead. He argues that the Fed's policies of the past three years, including the two rounds of bond buying known as quantitative easing, were potent enough to prevent a deflationary spiral.

Therefore, he says, we're back at the old conventional wisdom: Monetary policy should responding to short-term economic shocks, and fiscal authorities should avoid knee-jerk reactions that create uncertainty for workers and investors.

Bullard uses the analogy of two people in a car. If Mr. Monetary is tired and incapable of driving any longer, then Mr. Fiscal should take the wheel. You wouldn't, however, want both of them trying to drive at the same time.

A stimulus-minded politician might think of a different analogy: What about a storm-tossed ship that needs all hands on deck? "That's a misunderstanding of what's going on here," Bullard responds. "The literature is telling you they (fiscal and monetary policy) are substitutes, not complements."

Bullard is quick to note that his paper is a theoretical one, and that he's not taking sides in any partisan debate. He's also not taking a stand on whether any specific fiscal action, such as the $787 billion stimulus package of 2009, was good or bad.

He's not, in fact, saying that fiscal policy is impotent. He's merely arguing that it should have a long-term focus. "Set fiscal policy with an eye to the medium to long run," Bullard advises. "Stable tax and spending policy will promote investment and will promote economic activity, and we don't need to be getting into these fiscal stabilization efforts."

Bullard's ideas are likely to carry considerable weight, and he's building on work by Michael Woodford, an influential Columbia University economist. However, it's not hard to find thinkers like Paul Krugman, the Princeton economist and New York Times columnist, who continue to say the government hasn't done enough to stimulate the economy.

"Among academic-type economists, no, this is not controversial, but it is going to run up against the Krugman types," said Stephen Williamson, a Washington University professor who says he generally agrees with Bullard's thinking on fiscal policy. "It might stir things up a bit."

With a provocative title like "Death of a Theory," that seems to be Bullard's goal.