Spain votes Sunday in local and regional elections which will test Socialist Prime Minister Pedro Sanchez's chances of remaining in power after this year's general election.
In office since 2018, the stakes are high for Sanchez, whose party governs the eurozone's fourth-largest economy in coalition with far-left Podemos.
Of the 12 regions going to the polls, 10 are governed by the Socialists either alone or as part of a coalition.
These regional governments have been crucial allies for Sanchez, especially during the Covid-19 pandemic when he relied on them to impose restrictions on social life.
But the votes could mark "a turn to the right" whose magnitude could define the next general election, which has to be held by the end of the year, said Pablo Simon, political science professor at the Carlos III University.
The main opposition conservative Popular Party (PP) -- which has for months topped opinion polls -- has framed Sunday's elections as a referendum against Sanchez.
"It is only by voting that we can start to turn the page on 'Sanchismo'," PP head Alberto Nunez Feijoo said Tuesday, using a derogatory expression for Sanchez's policies.
Boosted by the near extinction of centre-right party Ciudadanos, the PP is confident it can win in six regions currently run by the left and boost its standing in Madrid, Spain's richest region.
Polls suggest the party is especially well placed in four regions: La Rioja and Aragon in the north, Valencia in the east and the Balearic Islands which includes the holiday island of Ibiza.
But in all these regions it would need the potentially awkward support of far-right party Vox to do so.
The PP has governed with Vox for the last year in the rural region of Castilla y Leon, where it has been regularly embarrassed by the far-right party's ultra-conservative positions on social issues, especially abortion.
Vox is "determined to join as many regional governments as possible to increase its visibility," said Antonio Barroso, an analyst at political consultancy Teneo.
"In contrast, the PP leadership would prefer to minimise the presence of Vox in regional executives to avoid controversial situations that might push the party away from the centre and potentially put off centrist voters."
Can the left resist?
PP leader Feijoo -- who won four consecutive regional elections in Galicia -- has sought to move the party to the centre since he became its national leader last year.
He has "sold himself as a moderate" but "does not know what strategy to adopt" towards the far right, said University of Zaragoza political scientist Cristina Monge.
Sanchez is trying to mobilise the left by warning of the risk posed by Vox and highlighting his government success in curbing inflation and steering the economy through the pandemic.
He has criss-crossed the country in recent weeks to announce new measures including affordable housing for the young, more healthcare funding and two-euro cinema tickets for pensioners.
"Economic indicators are good," said Monge, before adding that voters "don't have a vision that is as apocalyptic as the right's".
"The left is resisting better than expected," she said.
In the event that the PP wins the year-end national election but still falls short of a working majority -- even if it joins forces with Vox -- the Socialists could have a chance to stay on in government.
This is because small nationalist and regional parties "are still more inclined to seal deals with the left than with the right" in a fragmented parliament, said academic Simon.