Off-year elections such as Tuesday’s are notoriously unreliable markers in predicting the political future. Nevertheless, the results raised increasingly persistent questions about Mr Obama’s ability to transfer the excitement of his election victory exactly one year ago into legislative achievement, and on to other Democratic candidates.

Voters are yet to turn on Mr Obama himself — they still like him — but Tuesday’s defeats made clear that Americans are increasingly sceptical and unnerved by his policies, and disaffected with Democrats on Capitol Hill, where they control both chambers. No wonder Bob McDonnell, the victorious Republican gubernatorial candidate in Virginia, spoke of Democratic “overreach” in Washington.

Although it is highly unlikely that Democrats will lose control of Congress in next year’s mid-term elections — they hold a substantial 79-seat majority in the House and a 20-seat advantage in the Senate — if the unemployment rate does not drop significantly by then they are set for a heavy mauling.

Harry Reid, the Democratic majority leader, is already under pressure in his Nevada re-election race, and the mounting discontent over jobs and the economy cannot be helping.

In 1994, when nearly six voters in ten said they were unhappy with the economy, they backed the out-of-power Republicans over Democrats by 26 per cent — helping Republicans to capture 52 seats and control of Congress for the first time in 42 years.

A year after his historic victory, the excitement over Mr Obama and the belief in his power to “bring change” has largely abated. Voters said they wanted change, but a year on, with unemployment at 10 per cent, the change Mr Obama is prescribing — massive spending on health care, energy and education — is too much for many to stomach. If Mr Obama continues to lose the centre, he will be in danger of losing swing states like Virginia, Colorado and New Mexico that were crucial to his victory last year.

Tuesday’s results also provide growing evidence that the movement that swept him to power is already a diminished force, and was perhaps an extraordinary one-off coalition of the young, the African Americans and first-time voters at a time of hunger for a fresh face. The young were nowhere to be seen on Tuesday.

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