In the European Parliament elections, 2014, in Spain, two parties joined the EUL/NGL group: Izquierda Unida and Podemos. In recent polls for the Spanish general election, 2015, Podemos has risen sharply in the polls, perhaps stimulated by the success of SYRIZA in Greece.
Many countries in Europe have a single party in the EUL/NGL group, often a party with roots in eurocommunism or socialism. Although programs differ, they appear to have in common that they are to the left of the mainstream social-democrats (who are frequently in government), but have themselves not been part of any government on the national level. They might benefit electorally if the social-democrats are perceived by their traditional basis to compromise too far from their traditional policies. Some examples are Die Linke in Germany, Socialistische Partij in The Netherlands, Vänsterpartiet in Sweden — and Izquierda Unida in Spain.
It surprises me that the new progressive movement in Spain appears not to benefit Izquierda Unida, but rather the new startup Podemos. What are some significant programmatic differences between the two? Or is the virtual electoral success rather due to style and the perception of the people involved?