Based on last week’s debate, both President Obama and Governor Romney believe that squeezing the Iranians economically is the best way—and perhaps the only way—to end their nuclear-weapons program without resorting to a military strike. Of course, nobody knows if sanctions will actually work. But if the United States is truly serious about crushing Iran’s economy, it must pursue a more aggressive strategy, and it must put more pressure on Iranian trading partners.

That raises uncomfortable questions for the major importers of Iranian oil, such as China, India, Japan, and South Korea, but also for countries that have benefited from a recent surge in exports to the Islamic Republic, such as Argentina and Brazil.