Niall Ferguson is Laurence A. Tisch professor of history at Harvard University. His latest book is Civilization: The West and the Rest.

If there is one issue on which the rival candidates for the U.S. presidency agree, it's that America's global leadership will endure. Mitt Romney insistsit is not a "post-American century," while Barack Obama declaredin his State of the Union address that "anyone who tells you otherwise, anyone who tells you that America is in decline or that our influence has waned, doesn't know what they're talking about."

They must enjoy this kind of chest-beating in Beijing.

That a resurgent China poses a challenge to American power -- especially in the Asia-Pacific region -- has been clear for some time to those who know what they're talking about. The real question is whether the United States has a credible response. Should it apply some version of the "containment theory" that the late George Kennan recommended for dealing with the Soviet challenge after 1945? Or something more subtle, like the "co-evolution" suggested by former Secretary of State Henry Kissinger?

Leave aside the military and diplomatic calculus and consider only the economic challenge China poses to the United States. This is not just a matter of scale, though it is no small matter that, according to the IMF, China's GDP will overtake that of the United States within four years on the basis of purchasing power parity. Nor is it only about the pace of China's growth, though any Asian exporter forced to choose between China and America would be inclined to choose the former; their trade with China is growing far more rapidly than trade with the United States.

No, according to some commentators, the contest between the two Asian superpowers is also fundamentally a contest between economic models: market capitalism vs. state capitalism...