Spaniards vote in general elections on Sunday that were called when Prime Minister Pedro Sánchez lost his parliamentary majority in February.

Here is everything you need to know.

Bottom lines

• The most likely outcomes are a continuation of Sánchez’ alliance with the far left or a deal between the center-right and far right.
• Small regional parties could hold the balance of power.
• The outcome could have a big impact on everything from tax policy to the legality of assisted suicide.

Electoral system

All 350 seats in the Congress of Deputies and 208 of the 266 seats in the Senate will be contested.

The Senate is a relatively weak upper body. The lower house can override its vetoes with an absolute majority.

348 of the 350 seats in Congress are assigned proportionally to the provinces of Spain, with a minimum of two seats per province. The two remaining seats are allocated to Ceuta and Melilla, the Spanish enclaves in North Africa. There is a 3-percent electoral threshold in each constituency.

208 of the seats in the Senate are elected by popular vote. Each of Spain’s peninsular provinces elects four senators, giving small provinces more power, which tends to benefit the right. Ceuta, Melilla and the Spanish islands in the Atlantic Ocean and the Mediterranean Sea have twenty seats combined. The remaining 58 seats are filled by regional legislatures.

A brief history

After democracy was restored in the late 1970s, Spain was for decades almost a two-party system with the center-left and center-right frequently splitting between 70 and 80 percent of the votes. Catalan nationalists were able to exploit this division by giving one side or the other a majority in exchange for autonomy.

The far-left Podemos (“We Can”) and the liberal Citizens broke this duopoly in 2015, winning 35 percent of the votes between them. Neither the Socialists nor the conservative People’s Party were able to form a government, necessitating snap elections the following year. Still no party won a majority and eventually the Socialists abstained to allow the People’s Party, which had placed first, to remain in power.

The Socialists went through a leadership crisis in the meantime. Pedro Sánchez, who had opposed letting the People’s Party’s Mariano Rajoy stay prime minister, and who was blamed for the party’s poor electoral performance, was ousted by moderates, who argued for accommodation with the right.

But Sánchez was vindicated in 2017, when he won back the party leadership in an open primary and organized the first-ever successful vote of no-confidence against a prime minister, ousting and replacing Rajoy with the support of Podemos and regional parties, including those from Catalonia.

Unresolved issues

Sánchez’ fragile coalition fell apart in February, when the Catalan parties joined the right-wing opposition in voting against his 2019 budget.

The Catalans had demanded a legal referendum on independence for their support, which Sánchez refused.

Among the measures in his budget were:

• 22 percent raise in the minimum page to €900 per month.
• €1.3 billion extra for education.
• €1 billion extra for pensions.
• €850 million for disability and unemployment benefits.
• €600 million for housing.
• €300 million to expand paternity leave.

Altogether Sánchez proposed to raise spending 5 percent from the previous year, which — if the economy slowed down — could have put Spain in violation of EU fiscal rules. Countries that use the euro are supposed to keep their deficits under 3 percent of GDP.

Other unresolved issues include:

• Taxes: The left wants to raise taxes on big companies and banks. The right wants to eliminate inheritance tax and reduce the highest income tax bracket. The People’s Party further wants to bring corporate tax under 20 percent and abolish the estate tax.
• Pensions: Pension cuts and a raise in the retirement age to 67 have barely helped close the gap between what Spaniards pay into the social security system and what they take out. The difference grows by around €18 billion per year. The only party with a concrete plan to reduce the shortfall is Podemos. It wants the wealthy to pay more.
• Assisted suicide: The liberal Citizens claim they support legalizing euthanasia but nevertheless joined the conservative People’s Party in blocking legislation to that effect in Congress.
• Limiting immunity for politicians: The Socialists found little support in Congress for a constitutional change to achieve this.
• The exhumation of Francisco Franco from the Valley of the Fallen: The Socialists want to remove the former dictator’s body from the itself controversial monument. The right is opposed.

Parties and their leaders

Twelve parties are projected to win seats in the new Congress, five of which are small regional parties from the Basque Country, the Canary Islands and Valencia. I won’t cover them in depth but, as we saw in the outgoing Congress, they could end up playing a key role.

• Spanish Socialist Workers’ Party, with an allied but independent branch in Catalonia, was founded in 1879 and a major force in the Second Republic that was defeated by Franco in the Civil War. After the restoration of democracy, it formally abandoned Marxism, U-turned on NATO membership and eventually adopted “Third Way” social democracy. It remains more popular with working and union voters than other center-left parties in Europe. Under Pedro Sánchez, it has become explicitly pro-European, feminist and more willing to do deals with the far left than the center-right.
• People’s Party, allied with Asturias Forum, was originally constituted as the People’s Alliance by reformist veterans of the Franco regime. Under Mariano Rajoy, it cut public spending and reformed labor law to avoid the need for a European bailout. Rajoy’s refusal to negotiate with a growing Catalan independence movement exacerbated discontent in the region. His successor, Pablo Casado, has pulled the party to the right on abortion rights, Catalonia, Gibraltar and immigration.
• Citizens, allied with the tiny Union, Progress and Democracy and led by Albert Rivera, was founded in Catalonia in 2006 in opposition to the region’s independence movement. The party is reluctant to call itself liberal, but it mixes center-right economic policies with progressive social views and support for the EU.
• Unidos Podemos (“United We Can”) is a merger of the anti-establishment movement Podemos and small far-left parties. Its policies include introducing a basic income, withdrawing from international trade deals and abolishing spy agencies. It has also campaigned for nationalizing energy companies and withdrawing from NATO. Its leaders recently split. There is a division between purists led by the party leader, Pablo Iglesias, and pragmatists led by his deputy, Iñigo Errejón.
• Catalan separatists include the Republican Left, led by the jailed former regional vice president, Oriol Junqueras, and the center-right Together for Catalonia, the successor to the region’s long-governing, but now defunct, Democratic Convergence party.
• Vox (“Voice”), led by Santiago Abascal, was founded in 2013 but only gained popularity in the wake of Catalonia’s attempted secession from Spain in 2017. It proposes to abolish Spain’s system of autonomous communities altogether and argues for the return of Gibraltar. It also opposes abortion, feminism, gay marriage and immigration from Muslim countries.

Polls

• Support for the People’s Party has fallen steadily since the last election, in 2016, from 33 to 19-23 percent.
• The Socialists gained when Sánchez took over as prime minister in June and have been the largest party in the polls since with 27-29 percent support.
• The Citizens, who in mid-2018 surpassed the other two parties in the polls, are now back in third place with 14-15 percent.
• Podemos has fallen even deeper, from 21 percent in the last election to 12-14 percent.
• Vox is suddenly up since it won 11 percent of the votes in Andalusia in December. Presumably its supporters were previously reluctant to tell pollsters they were planning to vote for the far right. It polls at 10-12 percent.

Possible coalitions

• Socialists + Podemos + Catalans + other regionalists: Perhaps the Catalans will change their minds and support Sánchez again after the election. They are unlikely to get a more sympathetic prime minister.
• Socialists + Podemos + other regionalists: Would allow Sánchez to continue his anti-austerity agenda and likely maintain the status quo in Catalonia.
• Socialists + Citizens: This is the coalition Sánchez tried and failed to put together in 2015. Both the Citizens and the Catalan branch of the Socialist Party have ruled it out, which shows you Spanish parties are still new to coalition politics. Ruling out the centrist option before an election only gives the parties on the flanks more more leverage in negotiations to form a government.
• Citizens + People’s Party + Vox: Currently being tried in Andalusia, but the prospect of putting the far right in power nationally could scare away voters from the mainstream right. All three parties argue for the suspension of Catalan home rule.