Count Edward Luce of the Financial Times out if you’re compiling a list of pundits and prognosticators who believe Hillary Clinton faces an easy path to win the 2016 presidential election. Luce shares his skepticism in his most recent column.

Come the glamour of 2016, Hispanic, millennial, single female and African American voters will be back in force. All that Hillary Clinton need do – or whoever takes the Democratic nomination – is tick the right boxes and let demography fix the rest.

Such is the US left’s world view. It is also a measure of its intellectual poverty. Whatever liberals are smoking, it is no stimulant to new ideas. The left’s sense of destiny is based on America’s shift to a minority-majority nation within the next 30 years. As the white vote shrinks, each presidential race will be harder for Republicans to win. What is missing is a compelling reason for people to embrace Democrats, as opposed to rejecting Republicans. For the time being, the latter can be relied upon to offend minorities – notably Hispanics. But Democrats have remarkably little new to say about the future of America’s middle classes, regardless of ethnicity.

Without a credible economic plan, the US left risks being little more than a rainbow coalition. This is the danger facing Mrs Clinton’s candidacy. It is possible – perhaps even likely – that Republicans will select a nominee who has alienated so many Americans that he will be unable to compete in a general election. It is also plausible that Mrs Clinton will appeal to enough women, Hispanics and others to ensure her electoral maths are prohibitive. That is the working theory. Unless Mrs Clinton can find a positive story to engage America’s middle classes it is the only one that is likely to work in practice.

Of course, the notion of an inevitable Hillary Clinton presidency has been challenged before.