To understand Pedro Sánchez's victory in the contest for the leadership of the Spanish Socialist Workers' Party (PSOE) on Sunday night, we must first accept the existence of two external (but not far removed) driving forces that were mostly beyond the PSOE's control. Firstly, the economic crisis of 2008 and the collapse of traditional social democracy as a viable governing alternative across Western Europe; secondly, the rise of alternative left-wing parties or currents (Syriza, Podemos, Corbyn, etc.) in response to that first phenomenon. The economic environment within which socialist parties existed until Lehman Brothers went bankrupt changed and the PSOE in Spain, (New) Labour in the UK and PASOK in Greece were not able to articulate a response that satisfied voters. They did not adapt quickly enough to new times.

Until now, this has mostly been treated as a political problem but the depth of the crisis on the left leads us to believe the roots of the matter might lie far beneath the surface in socialism's historical attitudes towards the economy and the solutions socialist parties have not so far been able to offer 21st Century tax payers. Perhaps they will ultimately have to go back to before Marx and basic concepts of private property and capital. Opportunities are still to be found in public ownership of companies, the consideration of the public good and the sponsorship of innovation, for example, if the left is willing to throw its previous statist ideas in the bin, think anew and gear up for a fight with right-wing neoliberal capitalists. So far, no one on the left seems to have done that work in a satisfactory manner.

In Spain in 2014, those pressures came to a head with the sudden appearance in Spanish politics of Podemos, led by Pablo Iglesias, at the European elections, where the party won five MEPs. Alfredo Pérez Rubalcaba, then leader of the PSOE, announced his resignation the following morning, King Juan Carlos abdicated and King Felipe was proclaimed as the new monarch, and the Socialist Party chose a new leader: Pedro Sánchez. At the time, Mr. Sánchez was seen as the safer pair of hands and was backed by…Susana Diaz and the party's old-guard, against the Basque socialist Eduardo Madina, considered then as a potentially loose cannon on the issue of the continuance of the monarchy and the PSOE's republican roots.

Two years later, Mr. Sánchez had himself become a loose cannon and had obstinately dug in on the issue of rejecting Mariano Rajoy after a second general election in six months that was no more conclusive than the first one. Having stuck to his guns, he was unceremoniously ousted last year in a palace coup on October 1, backed by Susana Díaz and the old guard. The party was handed over to administrators aligned with the senior leadership and abstained in favour of a new conservative government led by Mariano Rajoy (PP) at the end of October. Sánchez resigned his seat as an MP and announced he was off on a road trip around Spain to reconnect with Socialist Party members. That strategy clearly worked, and he bested Mrs. Díaz and the entirety of the PSOE senior leadership—arranged against him as if on a medieval filed of battle—at the ballot box on Sunday by a margin of more than 15,000 votes. His victory was not just against her, but against two former socialist Prime Ministers—Felipe González and José Luis Rodriguez Zapatero—who had sided with the Andalusian leader. PSOE members rejected being told what to do by the party establishment and rejected the policy of abstaining in favour of Spanish conservatives.

All of that is what socialist MP (and Sánchez backer) Odón Elorza was referring to in his tweet on Sunday night about "the epic story" having won. It is a tremendous comeback for Mr. Sánchez. He is now reborn, politically speaking.

Notwithstanding the long-term economic philosophy problems, which Sánchez's victory is not going to solve, we are back to the main issue: power, and who holds it. We are back to where we were in September last year, to frontal opposition to Rajoy, to some form of rapprochement and more open rivalry with Podemos, and to an unstable political situation regarding the big questions of state. There are three pressing items. One is the motion of no confidence itself (imagine the nerves in Brussels and Berlin were it to prosper), another is the question of Catalan independence, and the third would be the 2017 budget. All three could now be newly problematic after Sánchez's victory.

That is perhaps why El País and Mariano Rajoy both decided to try to win back control of the news cycle on Monday morning with the Catalan question. El País published an "exclusive" on the regional secession bill Catalan separatists are preparing. The PP headlined its press release today with a quote from Mr. Rajoy on Catalonia: "We are not going to allow [Catalan First Minister] Puigdemont to threaten and blackmail the state". Headlines in Spain say he has rejected the idea of calling an early general election after Pedro Sánchez's victory, but, as a matter of fact, the Spanish Constitution says a Prime Minister may not dissolve parliament while a motion of no confidence has been tabled; which it has been, by Podemos on Friday. The Spanish Congress confirmed to The Spain Report on Monday that this is the case.

Spanish politics just got exciting again.