President Obama has responded to the political pressure to do something about the elusive oil spill one mile under the Gulf of Mexico by issuing a six-month moratorium on drilling in the Gulf. Today he predicted that the oil spill could have a "substantial" impact on the U.S. economy, but he defended his moratorium decision against concerns that it would exacerbate the damage to production.

THE PRESIDENT: When I made the decision to issue the moratorium, we knew that that would have an economic impact. But what I also knew is that there was no way that we can go about business as usual when we discovered that companies like BP, who had provided assurances that they had fail-safe backup, redundant systems, in fact, not only didn't have fail-safe systems, but had no idea what to do when those fail-safe systems broke down.

This is the safe decision, politically if not substantively. But as The Atlantic's Niraj Chokshi explained, the moratorium is not without risks:

The six-month ban on drilling in the Gulf of Mexico could encourage companies to move their rigs to other parts of the world, increasing the nation's reliance on imported oil. But it would also increase our reliance on long-distance shipping to bring that oil to the U.S. and increase the probability of oil being spilled at sea. Over the last half-century, transport vessels have been responsible for almost two-thirds of all marine oil spills, according to data arranged by Tulane University professors.