One rather partisan article does not make a rout.
Syriza appear to still have mass support and Spain is slightly different than Jenkins alludes:
http://www.nytimes.com/2015/05/26/world/europe/spains-local-election-results-reshape-political-landscape.html?_r=0
Far greater numbers than just the Left need to have a serious rethink (for many their first real think) : the world's labour supply has quadrupled in the last couple of decades due to globalisation with the opening of an international market system, putting pressure on the wages and conditions of people in Europe, the United States and Japan amongst others, and the share of national income going to Capital has gone up dramatically and the share going to labour has gone down.
This is unlikely to change as global financial entanglement/dependency is too far advanced, and unless the Left adapt to this they will be further marginalised.