Lately, I often meet people outside Spain who praise the prime minister, Pedro Sánchez. In Britain, Italy or the US, friends, acquaintances or random people who learn I am Spanish offer admiring words about his positions on Gaza and Iran. It’s understandable.

Sánchez spoke out against Benjamin Netanyahu and Donald Trump earlier and more forcefully than most European leaders did, with a powerful message on international law. And the Spanish leader has been one of the clearest and most effective advocates for immigration in one of the fastest-growing countries in the west.

Most Spaniards back Sanchez’s outspoken positions on Israel-Palestine and his economic case for immigration. So how can it be that his party, the centre-left PSOE, has just lost its fourth regional election in six months and appears headed for defeat in next year’s general election?

The results in Andalucía, the most populous region in Spain and one of the nation’s poorest, are particularly devastating for the socialists, who governed there for almost 40 years. The party’s first prime minister after Franco’s death, Felipe González, is from the regional capital, Seville, and the PSOE’s national successes in the 1980s were deeply rooted in Andalucía. On Sunday, María Jesús Montero, a former minister in Sánchez’s government, delivered the party’s worst result in the region since the restoration of democracy in Spain, securing just 22.7% of the vote – about half the tally the party was securing at elections in the 2000s.

The beneficiary of the socialists’ defeat is not just their traditional opponent, the centre-right Partido Popular (PP), but the far-right Vox, because the PP’s insufficient majority means it will need Vox support to govern. The PP’s own national corruption scandals and public health service mismanagement saw Andalucían president Juanma Moreno lose seats on Sunday too. Meanwhile the leftist, regionalist Adelante Andalucía emerged as the other unexpected winner of the election, going from two seats to eight.

The socialists’ result in Andalucía can partly be explained by local factors, such as the popularity of a mild-mannered conservative president and voter resentment toward a PSOE candidate perceived to have been parachuted in from the national government. But it’s also another sign of Sánchez’s weakening position.

The PP has been leading the national polls for more than a year now, amid corruption scandals involving former socialist officials and even Sánchez’s wife, who has been charged in a legal case brought against her by a far-right group – she denies any wrongdoing. And only this week, another major scandal involving a socialist grandee has emerged: a judge has put former prime minister José Luis Rodríguez Zapatero under investigation for alleged influence peddling. He too denies any wrongdoing.

All this is unfolding in a context in which every aspect of public life in Spain is hyper-partisan and highly contested. Even judges and journalists are increasingly drawn into political conflict, and it is often difficult to clarify the basic facts of any issue. The natural attrition that comes after eight years in power is another explanation for Sánchez’s declining popularity during a period in which so many incumbent governments have been struggling.

In Spain, the decline in trust in politicians and institutions is often fuelled by this constant confrontation between parties. This dynamic tends to demobilise voters, particularly on the left, as the Andalucían results suggest. Even the recent outbreak of hantavirus became an excuse for acrimonious political squabbles. After the Spanish government allowed the affected cruise ship, the MV Hondius, to dock in the Canary Islands, every aspect of the episode turned into a partisan spat, from (imaginary) infected rats swimming ashore to the World Health Organization’s response.

The irony is that beneath the toxicity of Spanish political debate, the country’s economy remains strong. Growth continues to exceed expectations, driven by exports, services and immigration. Sure, the cost of living is a challenge in Spain, as it is elsewhere: house prices are soaring in major cities and salaries have been flat for several decades. But energy bills remain lower than in Germany, France, Italy or the UK, thanks to the country’s heavy investment in renewable energy. Meanwhile, public transport is clean, affordable and extensive – and life expectancy is among the highest in the world.

Immigration, mostly from Latin American countries, has made Spain a more diverse and open society than ever before, while also helping to sustain economic growth and offset demographic decline. The far right is now refocusing its messaging on immigration, but some conservative leaders are reluctant to join the backlash. In some cases, they’ve openly pushed back against Vox’s xenophobic rhetoric.

Sánchez’s calculus is that enough Spanish voters will look at what the new rightwing regional governments do in power and come back to PSOE. Administrations where Vox are a governing party have already changed policies on immigration, gender equality and even bike lanes.

Spain’s next general election must be held by August 2027. Pedro Sánchez could still pull off a comeback, as he has done several times before. But the increasing fragmentation of Spanish politics and the weakness of the parties to the PSOE’s left will make his path to victory far more difficult this time. He has just one year left to turn things around.

• María Ramírez is a journalist and deputy managing editor of elDiario.es, a news outlet in Spain