In the three biggest European economies, all of which have governed their country (more or less) independently in the past, not one could convince in excess of a quarter of the electorate. The party still clinging to power in the UK did the worst, but the PS (in opposition) and the SPD (a junior partner in the governing coalition) did no better.
In fact, almost no PES affiliate Europe-wide actually came out of the Sunday as the largest party in their country (Greece, Malta and Denmark being the only exceptions), and only in a handfull did any of them poll more than 30%.
Now if it were in a few countries, then maybe I might think these had political explanations, just the usual toing and froing between the mainstream parties. But as a Europe-wide trend then it looks like the social democratic centre left could be going extinct.
Beneath the individual afflictions of different parties is their an underlying reason in our society for these parties to be drowning in the sea of history?
What sustained these parties over the course of the 80s and 90s was a mixture of things; the persistence, emotionally if not socially, of their historical base - the mass industrial working class - and the main other one was an ability to appeal to liberal-minded centrists in some sort of opposition to social conservatism and the worst excesses of neoliberalism. They succeeded by being a nicer version of the conservatives and hoping their traditional support didn´t notice.
Eventually of course their traditional support was going to notice that they were doing very little (if anything) in their interest, and either desert them, or (in the case of the younger generation) never turn to them in the first place. And the thing about all those centrists is that they´re fickle as hell, so they wander off as soon as something nicer and shinier comes along, or whenever it looks like this lot aren´t managing capitalism very well.
In the midst of a recession the problem gets exarcebated, because it´s their support that´s suffering, and they´ve nothing to tell them. Once you sign up for neo-liberal consensus there´s not a great deal you can do to support working people in a recession. So when it´s obvious the system isn´t working and you refuse to help people in any significant way, they start to leave you in even greater numbers.
With conservatively-minded people, especially economic, their support stands up even under globalisation and recession, because basically it doesn´t challenge any of their core beliefs. The problem are scrounging shower at the bottom, or, the mass of impoverished people who have now stopped voting. Your support base stays in tact and just asks that you do the same things only harsher. They wait for capitalism to sort itself out.