There are few more compelling but grisly rituals in British politics than the pursuit of a wounded party leader. Hostile commentators switch from scepticism to contempt. Dissatisfied party colleagues offer coded or not-so-coded criticisms, or ominous silence. Murmurs circulate about supposedly better potential leaders. Rival parties gloat. And everything about the ailing leader – every mannerism, every mistake, every interview, speech or initiative – is seen through the prism of their anticipated doom. That they are struggling becomes increasingly the only thing voters know about them.

Digital media have made this echo chamber even crueller. But the decades-old dominance of British political journalism by rightwing newspapers, with their rigid assumptions about how little left-of-centre thinking the British electorate and economy will tolerate, has shortened the shelf lives of Labour leaders in particular. Four of the party's last six – Michael Foot, Neil Kinnock, Gordon Brown and now Ed Miliband – have been widely written off as failures for much of their tenures. Another, John Smith, while revered in retrospect, was actually often portrayed as over-cautious and ineffectual during his brief leadership between 1992 and 1994. Only his successor, Tony Blair, arguably the most un-Labour leader of all, enjoyed years of respect and seeming impregnability. And he still had a hunted look by the end.

Yet Miliband's has been a beleaguered leadership even by Labour standards. From the moment he narrowly beat his brother David, the media's favourite, to the party leadership less than 16 months ago, he has been portrayed by many as a political dead man walking. "The [leadership] result is the worst possible for Labour," wrote the Blairite columnist John Rentoul in the Independent on Sunday the next day. "Ed was the 'cork-popper' candidate in Conservative HQ ... David Cameron, lucky general, faces an opponent with less of a mandate than Iain Duncan Smith."

Miliband leadership crises, real and imagined, have followed at regular intervals. No matter that he inherited a party that had just suffered one of its worst general election defeats; that after 13 years of the Blair-Brown government many voters were tired of Labour, and likely to remain so for a few years, whatever a new leader did; since September 2010, almost every Labour shortcoming, the conventional Westminster wisdom has it, must be Miliband's fault.

The last month has probably been his worst yet. In mid-December, after Cameron's crowd-pleasing EU veto, Labour's consistent poll lead under Miliband abruptly disappeared, just in time to colour the end-of-year political roundups, and to give the plotters and gossips renewed vigour over the Christmas recess. Then, early this month, with news at a premium, the Labour peer, Miliband adviser and loose cannon Maurice Glasman wrote in the New Statesman that his "leadership seems to [have] no strategy, no narrative and little energy."

Glasman's remarks set off a feeding frenzy. In the Daily Telegraph – like other Tory papers slyly hospitable these days to anti-Ed Labour voices – the blogger and David Miliband supporter Dan Hodges wrote that Ed was "not the new Bobby Kennedy, but the new Adrian Mole". On the Today programme on Tuesday, an even more aggressive interview than usual suggested Miliband might be "too ugly" to ever be prime minister. Three hours later, bookmaker William Hill announced it had cut its odds on him not leading Labour into the next general election "from 10/1 when he was appointed [sic] to a current price of just 2/1". Odds were also offered on a long list of alternative Labour leaders, including the shadow home secretary Yvette Cooper. On Thursday, the Spectator described him as "Cameron's best weapon". On Wednesday, Matthew d'Ancona wrote in the London Evening Standard that Miliband's only political achievement had been "sabotaging his brother's chances of becoming Labour leader".

The drama of that sibling contest has inevitably lingered over Miliband's leadership. But his tenure has had other potent themes. He has boldly condemned the "predatory" parts of capitalism, Blair's war in Iraq and the long, malign influence of Rupert Murdoch. He has shrewdly spotted the erosion of living standards for middle-income Britons and given it a successful populist catchphrase, "the squeezed middle". Under him, Labour has won every parliamentary byelection and increased its national vote share, even in the worst polls, by a quarter since the 2010 general election. Compared with the semi-chaotic performance of Labour after its 1979 ejection from office, and of the Tories in their first half dozen opposition years after 1997, it is a story of modest revival.

But it has not often felt like that. Miliband has a tendency to make mini-breakthroughs and then not follow them up. He is cerebral by the standards of modern politicians, and like an academic producing clever papers after long periods of studious silence, after each success he seems happy to disappear, rather than immediately raise his profile further – as better opposition leaders such as Blair and Cameron have done.

He often seems to overestimate how much time he has to rethink his policies and reposition Labour. On Today, defiantly contrasting the current "noises off" about his leadership with the date of the next election, he said: "The race will be run, probably, over five years." But a third of that time has already gone.

Meanwhile, he seems to underestimate the presentational side of his job. Last Saturday he told this paper, in characteristically roundabout fashion: "What is the most important thing for a leader of the opposition to have? It is to establish an argument about what is wrong with the country and what needs to change." That may be true; but effective prime ministers-in-waiting such as Harold Wilson and Margaret Thatcher have sold a mood as well as an analysis. In their tone and appearance, they personified change. With his insider's CV and policy-seminar geekiness, Miliband may just seem too much like a New Labour technocrat to convince voters that he is the fresh kind of centre-left politician he actually may be.

Could he make it to the general election, let alone win it? So far, he has faced an exceedingly lucky government, insulated from the consequences of its ramshackle radicalism by voter-distracting foreign calamities, domestic good news stories such as royal festivities, and by a freakish absence of byelections in vulnerable coalition seats. That luck is unlikely to last. If the economy does not properly revive before the election, or if the public sector cuts produce significant social upheaval, Miliband may not have to be an outstanding opposition leader to take advantage.

The alternatives to his leadership also look less appealing up close. For a recently defeated party, Labour has a surprising number of able politicians in their 30s and 40s. But none of them has found a formula, yet, to entice a Labour-weary public. Shadow cabinet ministers have struggled to get the country's attention even more than Miliband. Meanwhile, calls from the Blairites and their party descendents for a return to New Labour policies, now taken to mean a "realistic" – code for broadly supportive – attitude to the coalition's cuts and privatisations, seem unlikely to thrill an electorate that already has two austerity parties to vote for.

Finally, it should be remembered that Labour does not easily get rid of its leaders. Even Blair's decision to stand aside took years to drag out of him. Labour's lack of ruthlessness in this area could change: British politics, like British life, may be entering new territory. Whenever Miliband hits the buffers, whether soon or as prime minister, I suspect it will be his successor who truly reaps the benefits of his halting but brave effort to rethink Labour's place in the modern world. As a keen student of political history, Miliband will understand that process. But I'm sure he'd rather be Jesus than John the Baptist.

What Ed should do next

Gaby Hinsliff, former political editor of the Observer

If there's one adjective no politician wants near their name, it's "beleaguered", and Ed Miliband is dangerously close to beleaguered now. It's not entirely fair. Monday's speech showed he understands why many voters don't trust Labour on the economy, and has moved accordingly. As for the charge of being all vision and no beef, if anything there were too many complicated mini-pledges.

Miliband does complexity well; it's simplicity he lacks. Most voters are only half-listening at best, and all but the clearest ideas tend to slide over their heads – leaving vivid but unhelpful snippets.

It may now take something dramatic to break the downward spiral.

Mehdi Hasan, co-author of Ed: The Milibands and the Making of a Labour Leader

Miliband has been a poor communicator; he has major presentational issues. But what's the alternative? Replacing him with Yvette Cooper? That's supposed to solve all of Labour's problems? Come off it.

His critics forget that he inherited a party which had just suffered its second-worst election defeat in a hundred years. They should give him a break.

Meanwhile, Miliband has to ramp up his rhetorical assault on Britain's vested interests. If he isn't the voice of the little guy, he won't win in 2015.

John Kampfner, chief executive, Index on Censorship

In classically insular style, we think it's all down to us. We plucky Brits have all the problems … and the solutions. That Ed Miliband: if only he didn't look a nerd; if only he learnt to ad-lib better at PMQs, Labour would be in better nick.

The global financial crisis has been a setback not for free marketeers, as it should have been, but for the left. Ten years ago, half the EU's 27 member states were run by social democrats. Now it's four.

None of the Labour recipes of the past seem to have traction any longer, and the centre-right parties most closely associated with the failed economic model are most confident. The problem is about more than Ed.

Laurie Penny, New Statesman columnist and activist

It is painful to accept a leader is letting you down, especially a leader who was supposed to represent a change in the way politics is done. Many of the party faithful have long clung to the notion that Ed Miliband's problems are cosmetic; that he'd be fine if he just had a bit more media training, got married or learned to smile less like somebody trying to get the lid off a jar of jam.

But what Miliband lacks is not a nice nose or better hair; it's a spine. Right now, the country needs a leader, and a party, that can offer more than a mitigated programme of Tory cuts.

Neal Lawson, chair of Compass pressure group

Ed Miliband's rhetoric on predatory capitalism has been spot on, but he needs to have the courage to follow through with his convictions. Take his change of mind on the proposed European Financial Transaction Tax – he's gone from supporting it to saying it's unfeasible.

The Tories are ahead in the polling on the economy not because they present the right policies, but because there's a consistency to their message lacking in Labour. Leadership is not about looks, it's about ideas, and Ed remains the best chance Labour has.