This, in turn, points to the narrow basis around which Díaz had sought to reorganize the Spanish left from mid-2022 onward. Drawing on the coalition government’s experience managing the pandemic as well as her legislative achievements strengthening workers’ rights, Sumar looked to broaden the Left’s electoral appeal by presenting itself as a credible party of government — one capable of delivering concrete policy advances. In this respect, its profile chimed with the technocratic spirit of the early 2020s. This was a moment when Bidenomics and the European Union’s COVID-19 rescue fund appeared to open up the possibility of a new progressive state interventionism and when — very briefly — far-right populism was on the retreat.

As Sumar was rolled out across a series of public events in late 2022 and early 2023, Díaz struck a note of pragmatic reformism. Pointing to the coalition’s successful cap on energy prices and her reform cracking down on bogus self-employment in the gig economy, she insisted that through institutional negotiation and social partnership a new social contract for the twenty-first century could be achieved that would go beyond neoliberalism. Missing, however, was any role for grassroots organizing or a clear anti-elite discourse — with Díaz’s more managerial profile and her platform’s softer messaging striking a distinct note to Podemos’s combative left populism.

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Podemos founder Pablo Iglesias had in fact also failed to effectively combine his ministerial role with an oppositional discourse during his eighteen months in the cabinet, engaging in highly charged controversies around lawfare and media bias that alienated voters at the height of the pandemic. By contrast, Díaz became the highest-rated political leader in Spain after successfully overseeing the Spanish state’s COVID-19 furlough scheme and pushing through repeated increases in the minimum wage. Quickly becoming a household name on the back of these measures, she was able to appeal to a substantive part of PSOE’s vote despite being a member of the Spanish Communist Party and a Unidas Podemos minister. As Iglesias resigned and named Díaz deputy prime minister in 2021, many on the Spanish left believed her candidacy could see the parliamentary left expand its profile and weight in cabinet.

Reorganizing the Left to exploit this window of opportunity was core to Sumar’s tactical hypothesis. Yet ultimately Díaz and her inner circle were not able to build on this initial promise, failing to expand out from her popularity as a pandemic-era minister to construct a sustainable electoral brand or organization. Like Podemos before it, Sumar was built as a lean, top-down platform, but one which unlike its predecessor did not have its origins in a movement wave beyond the institutions but rather was built from office. This has further reinforced the sense that it is defined more by its promise of “effective” progressive governance than by any clear social or political identity.

Initially, Sumar struck a laborist line, playing up Díaz’s links to trade unionism, before pivoting to a pop-infused green discourse during the 2023 snap election and then slowly moving back toward a certain social and laborist message in recent months, after Errejón’s exit. But these discursive shifts occurred without it ever articulating a broader political project that went beyond its participation in government.

Even in the 2023 general election campaign, the first time Sumar’s machine was put into action, the platform struggled to cut through, with its policy-focused campaign lacking a clear narrative and coming across as overly technical to many voters. Though Díaz had made her name delivering bread-and-butter labor and welfare reforms, her green-aligned campaign advisers changed tack and instead focused Sumar’s campaign on innovative policies linked to free time, equality of opportunity, and mental health. In part, this was a means to distinguish Sumar from Sánchez’s pitch for social democratic stability, but proposals such as its Thomas Piketty–inspired universal inheritance scheme (under which every eighteen-year-old in Spain would receive €20,000 to “kick-start a life project”) failed to engage the Left’s base — with the young academics and professional consultants staffing the campaign unable to sell their policies.

Díaz’s strong performance in the final stretch of the campaign, particularly in the leaders’ debate, was enough to repeat the result obtained by the Unidas Podemos alliance in 2019 but not to win over PSOE voters in the earlier-predicted numbers. Indeed, amid a global reactionary wave, Sánchez bucked the wider trend of incumbents being punished over the cost-of-living crisis, not least because of the Spanish government’s more robust protection of working people’s living standards — which pressure from the Left had been key in securing.

Relief at avoiding a hard-right Partido Popular–Vox government was soon tempered, however, by the weakness of the second coalition’s numbers in parliament — with the administration now depending on the support of the center-right Catalan-nationalist Junts to have a majority to pass legislation. Over the last eighteen months, this pro-independence party has used its effective veto to stall most of the government’s agenda, including blocking the coalition from passing any government budget since the election. At the same time, the limits of the first coalition’s reform agenda have also become apparent, particularly in terms of its toothless housing law — with Spain’s largest cities facing rent hikes of 10–14 percent in 2024.

Yet faced with this changed scenario, Sumar has remained wedded to its progressive governance line, even as it finds itself operating in a political field marked by greater polarization and in which it is now unable to advance policy solutions. In part, this reflects the fact that Díaz had built the platform in her own image — instituting a clear out of Unidas Podemos’s front bench prior to the election and bringing in a series of little-known candidates with policy-orientated and professional backgrounds. The new MPs have not been able to generate their own media profiles or shown much capacity for political communication — as exemplified by the platform’s first parliamentary spokesperson, Marta Lois, whose restrained interventions during her brief five months in the job were simply drowned out amid the heightened atmosphere of current Spanish politics.

Ultimately, without the Left’s previous institutional momentum and Díaz’s ability to win high-profile policy concessions in the cabinet, Sumar has not been able to maintain a distinct political profile from PSOE over the last eighteen months. Junts has refused to support Díaz’s star policy proposal for a reduction in the working week from 40 to 37.5 hours while it has also voted down measures such as the renewal of the windfall tax on electricity companies’ profits and a vital reform that would have allowed for rent controls on short-term leases.

Political analyst Mario Rios doubts whether such measures alone could ever have sustained Sumar given the political direction of travel in post-pandemic Europe. “In the current political landscape, governance is necessary, but it is not the main tool for attracting voters and winning elections,” he explains in relation to Sumar’s positioning. “Today’s politics is based on the confrontation of models, values, and worldviews,” he continues. “In contrast, Sumar is based on the idea that voters simply want solutions to the problems they face. Focusing solely on policies like the minimum wage or the reduction of the working week without framing them as part of a broader vision can only lead to electoral defeat.”

Yet Sumar’s failure to flesh out its project and its lack of results in the cabinet cannot alone explain the collapse in Díaz’s popularity among the Left’s own electorate. Over the last eighteen months, she has gone from being the preferred choice for prime minister of two-thirds of Sumar’s 2023 voters to that of just 23 percent. There are now also considerably more Sumar voters from the last election who would prefer Pedro Sánchez to lead the government than her. Though her broader approval ratings are still much stronger than those of Iglesias when he stood down, only 40.9 percent of voters now give her a pass mark or higher, compared to 54.9 percent two years ago.

In this respect, her declining numbers with her own base and the platform’s disastrous European election results last year must also be seen in terms of Sumar’s descent into a spiral of internal crises and scandals. The platform seemed to have hit rock bottom the night of the European elections last June as Díaz resigned as its leader after it had only won 4.6 percent of the vote and three seats. She later clarified she would stay on as deputy prime minister and remain the Left’s figurehead in the government, but she would no longer lead the construction of a left-unity project.

At that point, however, her authority was already shot. The Communist-led Izquierda Unida, which had been Sumar’s most vocal backer only a year earlier, was now denouncing its “hyperleadership” structure and lack of internal democracy after it had been left without a seat in the European Parliament for the first time since its creation in 1986. “The time when Sumar set the agenda and other forces followed is over,” Izquierda Unida coordinador Antonio Maíllo insisted. Then Errejón’s resignation deprived the platform of its only other figure with national name recognition and opened up a firestorm of recriminations on the Left.

More broadly, however, the speed with which Sumar imploded has to be seen in terms of two factors relating to its internal development. First, it was constructed in opposition to Podemos. Second, reorganizing the Spanish left around such a personality-centered platform left it dependent on Díaz’s continued popularity, with Sumar, like Podemos before it, skipping the hard work of on-the-ground organizing during its initial surge, when it still had momentum.

In terms of the first point, Podemos’s responsibility for three years of debilitating factionalism should not be ignored, not least the way Iglesias named Díaz as his replacement as deputy prime minister via social media without even consulting her. At that time, Iglesias seemingly calculated that without any power base of her own, Díaz would operate as an independent figurehead while remaining dependent on Podemos. But in reality, Podemos itself did not have a robust grassroots infrastructure that could have operated as a solid launchpad for her candidacy — beyond, maybe, its media platform, which came to be Canal Red.

As Díaz sought to distance herself from the party and institute a broader renewal of the left-wing space, Iglesias, Montero, and Belarra reacted with increasing hostility. Yet her response to Podemos pressure has been repeatedly disproportionate, and rather than seeking a viable working arrangement in the run-up to the 2023 elections, when the party was at its weakest, she bet on seeing off its existing leadership — as she vetoed Irene Montero, its most prominent active figure, from running on Sumar’s list. In doing so, she overplayed her hand and underestimated the party’s ability to survive as an independent force on Sumar’s left flank — albeit in a very reduced form, with Podemos winning 3.3 percent and two seats in the European elections.

Moreover, Podemos’s new position on the opposition benches has also further complicated the options open to Sumar tactically. As political analyst Sergio Pascual notes, “Sumar now finds itself caught in a pincer movement between PSOE and Podemos. On the issues dominating the current agenda, like Gaza, rearmament, or housing, there is very little space left for it to occupy between Sánchez’s broadly progressive positioning, however timid in substance, and Podemos’s left-wing maximalism.” “Sumar’s mild, very rational messaging cannot gain traction,” he continues. Rios agrees, noting that “even if Sumar wanted to mobilize voters further on the left by, say, leaving the coalition over issues like military spending or housing, it would gain very little electoral advantage because it now faces a more radical rival, which is better positioned to channel this frustration and anger from the Left.”

It was in this difficult context that Sumar held its second national conference on March 29–30. The event had been delayed by nearly four months because of the Errejón scandal, with Sumar’s former spokesperson having been writing its new political strategy document as the allegations against him came to light. Coming under fire for her handling of the scandal, Díaz faced a major internal revolt from the various parties within her electoral alliance who insisted that Sumar was no longer fit to act as the unifying force for the parliamentary left.

The conference saw Sumar accept a reset of relations with its allies as it formalized its status as a simply another political party, without its previous pretensions to also incorporate other forces within its umbrella platform. Now with two little-known Díaz loyalists named as its new leaders, Sumar’s horizon will largely be limited to constructing a power base for the deputy prime minister. This means creating an organizational basis from which to negotiate her place and that of her front bench within a new left-wing electoral arrangement expected before the next elections — and in which Sumar will no longer play such a defining role.

Details remain scarce, but Izquierda Unida’s Maíllo has proposed a new alliance of “equals” in an attempt to avoid complete fragmentation of the left space. Yet the big unknown remains the ability of Podemos and the remnants of Sumar to work together. In its current role as the left opposition to the coalition government, Podemos seems convinced that it has more to gain by going it alone in the next election. However, this could change depending on polling and whether a unity list could be decisive in avoiding a right-wing majority.

“Right now, I don’t see any genuine interest from either side to move closer to each other, and so any negotiation will have to be pushed by other actors in this space, such as Izquierda Unida or maybe the trade union Comisiones Obreras,” argues Pascual. For Rios, the initial Sumar project “is already dead.” But he insists that “the main beneficiary of a divided left will be the far right, which will strengthen its relative position [in terms of seat allocation].” “Goodwill is now required from all those on the alternative left,” he continues. “Otherwise we are facing the prospect of a reactionary right-wing government at a time of global democratic decline.”

Such an election is not on the immediate horizon. Yet unable to pass a government budget, and with Spain facing further cost of living pressures, Sánchez is unlikely to go the full four years. The other unknown is Díaz’s own future and her readiness to continue in frontline politics beyond two terms in government and in a new alliance not of her own making. In its current shape, however, Sumar would be unlikely to survive in any form without her. This was underscored by the small scale of its conference, which amounted to a few hundred people in a midsize theater — quite distant from the thousands that packed out its launch event less than three years ago.

Many of those initially enthused by Díaz’s leadership had been left siloed in Sumar’s Telegram messaging groups, with no avenues open to them for formal membership or participation during the platform’s first two years. By the time it got around to doing some basic organizing in the wake of the European elections, the energy had already been sucked out of the room.

In reality, this is a familiar story on the Spanish left. A series of internally diverse left-wing projects have experienced initial electoral surges over the last decade — from Podemos at a national level and municipalist platforms like Ahora Madrid and Zaragoza en Común to Díaz’s previous En Marea vehicle in Galicia. But operating in an organizational void, most have very quickly come undone under external pressures and internal tensions. Any sustainable future project for Spain’s left will need to transcend this “electoral war machine” model. It seems unlikely that Díaz will be leading it.