London

IT is a safe bet that Asian currency intervention was not on the minds of Republican primary voters in Delaware this month when they selected a Tea Party favorite, Christine O’Donnell, as their Senate candidate. But the pendulum swings in American politics are a key concern of Wen Jiabao and Naoto Kan, the prime ministers of China and Japan, respectively, who both met with President Obama in New York on Thursday, with the loss of American jobs to Asian competition high on the agenda.

The Asian nations’ interest in American politics stems not just from America’s standing as the sole global superpower, but also from a growing belief among Asian leaders that the era of United States hegemony will soon be over, and that the polarization of its politics symbolizes America’s inability to adapt to the changing nature of global capitalism after the financial crisis.

What does this sweeping statement have to do with the price of yen? Plenty. On Sept. 15, the yen dropped sharply against the dollar, improving the competitiveness of Japanese exporters. After a brief bounce last week, expect the downward trend to continue. Mr. Kan’s government has decided to follow the lead of China and other Asian nations in “managing” (some critics would say manipulating) its currency; it spent a record $23 billion in a single day on foreign exchanges  the largest such intervention ever  instead of leaving the yen’s value entirely to market forces.

To understand how this decision will affect the United States, we must start with parochial politics  not in Delaware, but in the larger parish called Asia, which remains terra incognita to most American politicians and voters.