With the Labour Party polling at around 24 percent in the UK ahead of elections in June and France's Socialist Party on about 10 percent before Sunday's presidential poll, what has happened to the once mighty European left?

DW asked Mark Blyth, a professor of international political economy at Brown University in the US state of Rhode Island, if this year could mark the end of center-left parties in the advanced capitalist West?

"Yes and no," he starts.

"No, because there has to be an alternative and eventually the Conservatives [in the UK] will either screw up badly or be hit by events that push them out," Blyth says, adding that UKIP (the UK Independence Party) and the Liberals (the third-largest party) are not credible alternatives.

"Yes, because this is happening to all the major left parties in Europe," Blyth goes on. 

There are of course long-term structural - economic, sociological and demographic - reasons for the decline of social democratic parties. 

'Can't learn from their mistakes'

But there is also the more disquieting fact that center-left parties held power across swathes of Western Europe and the US from the 1990s through to the mid-2000s.

"The response to the recession from social democratic parties was largely to implement the austerity policies of the right," Sebastian Royo, a professor of Government and acting provost at Suffolk University in Boston, Massachusetts, wrote for online journal "Social Europe" on April 20.

Blyth concurs. "There are two reasons for this [decline]: the [social democrats'] move to the center in the 1997-2007 period meant abandoning their core, which has neither forgiven nor forgotten and the center has left them," he says.

"Second, they are also the 'helper apps of neo-liberalism.' They refuse to admit that they got that wrong and hurt their core. So they can't learn from their mistakes. Think Clinton in the US," he adds.

UK: Corbyn wheels out old demons

British Prime Minister Theresa May has called a June election as she seeks to increase her majority of 17 in the 650-seat House of Commons ahead of Brexit negotiations. The main reason she chose to do so now was, many agree, Labour's weakness. 

The 2016 Brexit vote to leave the EU effectively split Labour's support base, divided between pro-EU inner city voters - especially in London - and working-class voters in less affluent areas who tended to vote in favor of Brexit.

Blyth believes Labour should start by defining who and what is to blame. "Admit past mistakes," he says.

But current party leader Jeremy Corbyn never supported Tony Blair's New Labour and has said he has nothing to apologize for.

The foundations of Corbyn's approach seem to rely on a combination of a quasi-Marxist language of class conflict, exploitation and false consciousness, combined with doses of Puritanical moral indignation and disdain for material wealth and ostentation - an odd mixture and one that appears far from electability.

"How dare they crash the economy with their recklessness and greed and then punish those who had nothing to do with it?" he said, referring to the 2007-2009 financial crisis.

France: Monsieur Melenchon, the French Corbyn?

Two days before the first round of voting in the French presidential election, most polls show the Socialists facing crushing defeat. The party of President Francois Hollande - which came to power in 2012 with 28 percent first-round support and 51 percent in the runoff - is now on 7.5 percent.

"We are in a very bad situation, yes it's true," Socialist Party spokesperson Corinne Narassiguin told DW in an exclusive interview on DW's Conflict Zone this week.

France's main left contender is now Jean-Luc Melenchon. The Communist-backed candidate saw a last-week surge in popularity, overtaking conservative Francois Fillon and coming within touching distance of far-right leader Marine Le Pen and centrist Emmanuel Macron.

Germany: Even dead cats bounce

Support for the Social Democrats (SPD) in Germany has picked up since the party named Martin Schulz as its candidate to run against incumbent Angela Merkel for chancellor in September.

But this surge in popularity has waned - a recent Forsa survey showed support for Schulz under the 30 percent level for the first time in that poll since he was picked as the SPD's chancellor candidate.

Merkel's conservative alliance of her Christian Democrats and its Bavarian sister party, the Christian Social Union, is on 36 percent.

The Greens are polling at their lowest level in 15 years, dimming hopes that a left-leaning coalition may unseat Merkel. Polls show the Left party had 9 percent support.

What should the left do and does it matter?

"They either return to their Keynesian roots and offer hope and solutions to the young and their own traditional voters, or the populist parties will and they will be left out on the margins," Suffolk University's Royo writes.

And yes it matters, Royo adds: "The future of our liberal democracies is at stake."

Wolfgang Streeck, a professor at the Max Planck Institute for the Study of Societies in Cologne, agrees that this is far more than just the demise of one particular historical movement. "Socialism and trade unionism have prevented capitalism from destroying its non-capitalist foundations - trust, good faith, altruism, solidarity within families and communities, and the like," he told DW.