Gordon Brown’s administration has the look of a government drowning. A defeat in this week’s Crewe and Nantwich by-election would leave many wondering whether the prime minister can regain dry land. Beyond Britain’s shores, though, the world is turning faster. If Mr Brown can find a moment to escape the domestic tumult, the economic clouds are lined with a foreign policy opportunity.

Any day now we should have confirmation that Barack Obama will face John McCain in November’s US presidential election. In the long term, the nature and outcome of that contest may well carry much greater significance for British politics than a cliffhanger by-election.