Today’s by-election in Oldham West and Royton is the first real test for Jeremy Corbyn as Labour leader. Nigel Farage has said the results will be 'very, very tight', but a victory for Ukip is unlikely. They'll probably come a closer second than they did in May to the late Michael Meacher, but that says as much about the Tories' inexorable fall in England’s north as it does about the parliamentary opposition.

Oldham aside, meaningful insights into Corbyn's leadership are rare. Most of the media are biased against Labour’s unlikely frontman, and the political terrain after the Paris attacks has demanded he focus on areas – foreign policy and terrorism – where public opinion is least likely to agree with him.

A YouGov poll published towards the end of last month paints an alarming picture for the Labour leader. Corbyn’s low personal approval ratings are to some extent unsurprising, given the way he's portrayed by the media. Yet on close inspection the details of the polling data are worse than might be expected, even for his most ardent supporters.

If the European left is to replicate the Democrats' success in the US since 2008 – but with a more populist and radical programme – it needs to build on an electoral coalition of BME voters, women and the young. During Corbyn’s campaign this summer there appeared to be the beginnings of that: the party’s 150,000 new members tended to be younger and female, with the average age of the membership falling by eleven years in a few months.

That is reflected in November’s poll, with 18 to 24-year-olds, women and ethnic minorities tending to approve of the Labour Party and disapprove of David Cameron. But they all also tend to disapprove of Corbyn personally. That is particularly surprising among young voters who display, across nearly every issue, more progressive views than the rest of the electorate, and are more likely to approve of the Labour Party than not. David Cameron plays his voting blocs – the over-sixties and homeowners – like a fiddle; the politician who wants to introduce rent caps is unpopular even among private renters.

Labour’s only chance of forming a government in five years time is with a dramatic increase in turnout, something behind both Barack Obama's wins (turnout in the 2008 US presidential election was 7 per cent higher than in 2000) and the SNP’s Westminster breakthrough in May. Without women, ethnic minorities and the young supporting Labour there is no chance of that happening.

Three months into Corbyn's leadership, the energy that characterised his revelatory summer is on the wane. Some of that was inevitable, but his operation has also become too risk-averse. The outstanding use of social media before September – I’m told it accounted for more than £100,000 raised in campaign funds – has ebbed, and the way it was integrated with offline rallies is now a thing of the past. Labour’s biggest asset right now is its 400,000 members. How are they being leveraged to forge a counter-narrative through social media, raise funds or target Tory marginals?

When I interviewed Corbyn in July, he struck me as a superb candidate for networked activism and digital media simply because he was so open to new ideas. That openness seems to have gone, presumably because of the retinue that now surrounds him. The Labour leader could be a hugely disruptive politician in 21st-century Britain, but if his tenure is confined by the technologies and attitudes of the 20th-century left, he stands little chance of convincing even those who, on the face of it, are waiting to be inspired.