His economy is growing, he faces no criminal charges – unlike his opponent – and his fund-raising is going well. Yet Joe Biden’s battle for re-election as President of the United States now faces a surprise new threat – the surging price of petrol. Since the beginning of this year US “gas” prices have surged from just over $3 a gallon to $3.67 – a roughly 20pc increase. It’s still far less than we pay in the UK – equating to about 80p per litre – but fuel prices are among the most potent of political issues in the US. “Nothing terrifies a sitting American president more than a surge in pump prices during an election year,” Bob McNally of Rapidan Energy, a former adviser to George W Bush, told the Financial Times last month. It is why Washington has repeatedly warned Ukraine to halt its attacks on Russian oil refineries and begged Israel not to escalate the Middle East conflict – fearing either could prompt a jump in oil prices. Fuel is such an emotive issue because Americans tend to drive much longer distances than Britons. Pump prices are displayed far more prominently along US highways and often viewed...