The new PSOE, under the leadership of Pedro Sánchez, advocates a "plurinational" and "asymmetrical" federalism. Logically, this bet could win him the support of voters and nationalist parties, especially in Catalonia and the Basque Country. But beyond the internal politics of the PSOE, what would this federalist approach imply, on a practical level, for the organization and distribution of political power in Spain? At the end of the day, is it a mere reaffirmation of the status quo, dressed up in words that sound good to Catalan and Basque ears, or is it an ambitious program of constitutional and political reform?

It is not easy to interpret the practical meaning of the PSOE's federalist declarations, because in reality the language of federalism and even of "plurinationality" is notoriously ambiguous, compatible with a huge range of political solutions.

The concept of a "federal" union is derived from foedus, Latin for "treaty" or "pact". Traditionally a federal union was a compact between independent nations, like an international treaty. This was the case for the Confederate States of North America prior to their incorporation as a federal nation in 1789.

Those who opposed the new American constitution were called "anti-federalists" because in that historical and political context federalism had already acquired a more demanding meaning than a mere pact between sovereign nations. It already meant rather an incorporation of distinct states under a common government without their losing their sovereignty. The new federalism implied not only an external relationship between governments (as in the case of the old federalisms), but a common government, and furthermore, a common government that had a direct relationship with the citizens of its constituent States. A federal State was, under this new perspective, essentially a "State of States", in which political authority or sovereignty was shared between the "federal" State and its constituent States. This is more or less what is understood today by "federalism".

Some federal states, such as the United States, have been instituted under the banner of a single nation. Other federal states, such as the United Kingdom, Canada, and Switzerland, are plurinational, implying that their political units officially embrace different cultures and national identities. In some cases, plurinationalism implies not only a plurality of nations within the federal union, but also a plurality of nations within the same (more or less autonomous) states that constitute the federation, as in the case of the United Kingdom, one of whose constituent territories, the north of Ireland, allows its citizens to choose between English and Irish citizenship.

To constitute itself as a federal, plurinational and asymmetrical state, in line with the federalist policy of the PSOE, clearly implies the existence of a common government that shares political power with several more or less local governments. A plurinational federalism implies the official recognition that the various political units constituting the federation have different cultures and collective identities, worthy of some official and programmatic recognition subject . An asymmetric federalism implies that the relations between the general government and the governments incorporated into the union are flexible and adapted to the specific circumstances, needs, and historical contexts of each unit of the federation.

It is clear that a federal, plurinational and asymmetrical Spain is not a totally centralized and mononational Spain, nor is it a federation whose intergovernmental links are homogeneous. But as soon as we descend from these abstractions, we find that these concepts leave room for a very wide range of possibilities.

Under a more or less conservative interpretation, to defend a plurinational and asymmetrical federalism is no more than recognizing the current political reality in Spain, namely, that it is a culturally, politically and linguistically diverse country, and that the distribution of its political power will inevitably be complex and conditioned in part by the demands and historical situations of its various autonomous (or, to speak correctly, semi-autonomous) regions. From this perspective, the PSOE's statements reveal nothing new: they do nothing more than explicitly recognize the political status we inhabit.

On the other hand, a radical interpretation of these concepts would lead us towards a Spain whose semi-autonomous regions are endowed with a level of financial and political independence that approaches, more or less rapidly, the level of independence of a sovereign nation. Under this interpretation, Spain would go from being a constitutional monarchy constituted by a more or less consolidated central government, together with semi-autonomous regional governments, to being a league of nations, some of which with a high Degree of independence, loosely coordinated by a federal government (whether monarchic or republican), authorized to defend its vital interests, such as security and public order. If the PSOE had this interpretation in mind, it would be advocating an authentic constitutional revolution.

It is very unlikely that the PSOE is betting on this option, among other reasons because, at least for now, the Spanish electorate is not willing to approve such a radical change. However, the political gulf that exists between the two interpretations mentioned above should inspire some caution when interpreting a vague affirmation of federal principles such as that of the PSOE.

At the moment of evaluating any pro-federal proposal , we should take into account that there are not only the conservative and radical interpretation outlined above, but a myriad of intermediate interpretations, for example the granting of new powers to the autonomies in the economic and financial sphere, the restructuring of the tax system in favor of economic decentralization, and the decentralization of basic functions such as Education, health and social security. Until the PSOE presents a detailed program of political and constitutional reforms framed by a distinctive and elaborated vision of a "federal Spain", it will be impossible to assess the content and practical implications of its concept of "plurinational and asymmetric" federalism.