It’s 3am and your children are asleep, and the markets are collapsing in Shanghai, and in the White House a phone is ringing. Who do you want to answer it? With the collapse of the credit markets, the gyrations in energy prices and the surge in unemployment, this is becoming the central test facing America’s presidential contenders.

Neither John McCain nor Barack Obama began as an obvious candidate to answer the phone the way Bill Clinton was in America and Tony Blair was in the UK. Neither vice-presidential nominee, Joe Biden or Sarah Palin, is an obvious back-up to answer it either.