Anyone wondering why President Barack Obama has only now decided to push for immigration reform should look at the poll numbers. Mr Obama, who will give a speech on the 1 July calling on Congress to pass a bill giving the country's 11m illegal immigrants a “pathway to citizenship”, has proved a disappointment to Hispanic Americans – the fastest growing segment of the US electorate.

During the course of 2010, Mr Obama's approval ratings among black Americans and white Americans have not budged an inch, sticking at 91 per cent and 41 per cent respectively over the past six months, according to Gallup. Among Hispanics, by contrast, his numbers have dropped by 12 points to 57 per cent.

Ominously for the Democrats, the other group showing growing reluctance to turn up at the polling booths in November is the youthful millennial generation, whose enthusiasm, together with that of Latinos, was decisive in giving Mr Obama and his party a sweeping majority in 2008.