Ihear a recurring refrain from China these days: America’s strength comes not from its democratic and free-market values, but merely from the size of its economy and the power of its soldiers and weapons. There is nothing universal about America’s democratic and economic ideals, Chinese officials insist. Democracy is a relative concept, and markets have a centuries-old habit of spinning out of control. The US remains a superpower only because its economy remains on top. Soon, they warn, this advantage will be gone.

It is no surprise that many Chinese love this argument. It flatters their system and their current success. No need for genuine pluralism or large-scale privatisation of state-owned companies. China’s economy will soon surpass America’s; so say economists on both sides of the Pacific. So, is America exceptional because it is strong, or is it strong because its values are exceptional? That is a question the next president must answer.

It is accepted wisdom that America is in decline, but what about its strengths? Its economy is not simply the world’s largest; it is twice the size of second-place China’s, and its per capita income is higher than those of China, India, Russia and Brazil combined. For all the worry over the US credit rating and emerging alternatives to the dollar, global volatility has only reinforced its dominance as the reserve currency. America’s military is not simply the most capable. It is the only force that can project power in every region. Washington spent more on defence in 2010 than the next 17 nations combined, and even significant expected cuts won’t much narrow that advantage.