The Tea Party movement that is stirring up US politics means different things to different people. The intended reference is to the Boston Tea Party, the anti-tax, anti-colonial rebellion that sparked off the American revolution.

To British ears, the movement brings to mind another famous tea party – the Mad Hatter’s Tea Party in Alice in Wonderland, whose convenor spoke in illogical and exasperating riddles. To many foreigners and American liberals, the Tea Party does indeed seem like a crazy mix of wild conspiracy theories (Barack Obama is a secret Muslim) and impractical nostalgia for an era of distant and minimal government. Shortly before leaving for the US to report on the midterm elections, a respected colleague told me that: “Obama’s problem is that he is trying to govern a nation where half the population is insane.”

On closer inspection, the truth seems more complicated and less alarming. With unemployment stuck near 10 per cent, Americans are mad as hell, rather than plain mad. The Democrats are likely to do very badly in the midterm elections next month, and may lose control of both houses of Congress.