HORSHAM, England — “The Labour Party needs to be saved,” Angela Eagle, one of two rival "unity" Labour candidates, said as she launched her leadership bid against party leader Jeremy Corbyn.

A noble sentiment indeed. But the notion that replacing Corbyn with someone from the sensible wing of the party will save it from oblivion is hopelessly naive. The decline and fall of the Labour Party cannot solely be traced back to one man’s feckless leadership.

Rather, it is a long tale, played out over decades — and one of many chapters in the story of the slow collapse of the European social democratic Left.

From 1945 to 2010, British Labour’s share of the vote in national elections fell from 49.7 percent to 30.5 percent. In Germany, the Social Democratic Party won 25.7 percent of the vote in 2013; a dramatic fall from its best performance under Willy Brandt, when it captured a 45.8 percent share in 1972. The Social Democratic Party of Austria has seen its portion of the national vote almost halve from the height of its popularity in the late 1970s under Bruno Kreisky, as has the Spanish Socialist Workers' Party when compared to the early 1980s. The Panhellenic Socialist Movement in Greece has almost been wiped out, while the Socialist Party in France and Israeli Labor Party face uncertain futures.

Today, the British Labour Party, too, is in complete disarray. The parliamentary faction has no confidence in its leader. Corbyn's right-hand man, John McDonnell, has openly called his colleagues “f--king useless.” There aren’t enough cooperative parliamentarians to fill the Labour shadow cabinet. A leadership challenge is underway, but Corbyn’s opponents are divided between the equally uninspiring Eagle and Owen Smith. All three set out their vision for the future of the party on Monday, but the party seems as divided as ever.

With Corbyn now guaranteed a place on the ballot, the composition of the party membership and the prospect of further entryism from Momentum activists and other far-left saboteurs mean he is likely to be reelected, regardless of whom he faces.

However, Labour, eight points behind in the polls and with Corbyn’s approval rating at record lows, is destined for electoral defeat, whether that vote takes place in May 2020 or the spring of 2017. Before or after such a result, Labour’s mainstream could part ways with Corbyn’s far-left cadre, cleaving the Left opposition in twain.

Under Corbyn, the party as we know it is doomed to failure — perhaps even non-existence.

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Europe's social democratic parties have fallen on hard times for several reasons: acute pain of austerity and the rise of alternative leftist factions in Spain and Greece; the refugee crisis and the growth of the far-right in Austria; security issues and the Israeli-Palestinian conflict. But the fate of the British Labour Party is indicative of how, as the Guardian’s John Harris observed, “as with the center-left parties across Europe in the same predicament, Labour is a 20th century party adrift in a new reality.”

The structures and institutions that supported the social democratic Left have collapsed: working men’s associations, English non-conformist Protestant churches, and — perhaps most importantly — the trade union movement.

Trade union density — the percentage of total wage and salary earners that are trade union members — has fallen in Britain from 51.9 percent in 1981 to 21.5 percent in 2014. Rates of unionization have also fallen in Austria (27.8 percent, an astonishing 40 point drop compared to 1960), Israel (22.8 percent), Germany (18.1 percent), Spain (16.8 percent), and France (7.7 percent). The parties of working people have lost their workers.

The decline in unionization is both a cause and a symptom of the changing nature of labor. For the British working class, the past 35 years has meant the loss of hundreds of thousands of steady jobs in mining and heavy industry, replaced with unskilled labor jobs in warehouses, call centers and supermarkets. Zero hours contracts, agency work, and various forms of self-employment have taken precedence over collective bargaining and jobs for life.

Labour under Corbyn has ceased to represent the working class in any meaningful way

Unemployment has dealt as heavy a blow to support for social democratic parties — but so has the increasing lack of stability and security in employment. European labor parties have yet to catch up to this fundamental change.

When Margaret Thatcher remarked in 1987, “There's no such thing as society. There are individual men and women and there are families,” it wasn’t so much an observation as a terrible prophesy — one which would have terrible consequences for the Left.

Values among working people have also shifted. Social solidarity, egalitarianism, and fraternity, the founding ideals of social democratic politics, have withered away. The ultimate victory for Thatcherism was a psychological one.

The social democratic Left has always been an amalgam of the working and intellectual classes — students, academics, artists, and so on — marching together for the betterment of society. Increasingly, these two groups are like horses pulling in opposite directions.

Labour under Corbyn has ceased to represent the working class in any meaningful way, preferring ideological dogmatism and the cozy insularity of rallies and street demonstrations to organizing and maintaining a political presence in parliament.

Without a compelling reason to vote for the social democratic Left, working class voters across Europe are increasingly attracted to the anti-immigration, anti-European politics of the U.K. Independence Party, France’s National Front, and the Freedom Party of Austria.

A change of leadership would undoubtedly give the British Labour Party a boost, but Eagle, Smith, or whoever next takes the reigns will have to grapple with these structural issues. Labour’s fate is tied to that of the wider European social democratic Left.

If the new leader of the British Labour Party does not seriously reflect on how the party can best represent the interests of the weak and the working class in a changing economy, there will be no hope of turning around the party's fate. Their job will merely be to manage its terminal decline.

Liam Hoare is a journalist based in the United Kingdom, and a contributor to Moment Magazine.