Voters in Spain have put two outsiders in the office of mayor in Madrid and Barcelona. Both are strong, popular figures heading parties associated with the new Spanish left. Both are women. The similarities between the two candidates and the two cities end there.

Manuela Carmena, 71, is from a well-to-do family with an apprenticeship in traditional left-wing politics. She avoided being assassinated by neo-fascist gunmen during the 1977 Massacre of Atocha: a last-minute appointment change meant she wasn't at her law office when they stormed it, killing five of her colleagues in an event that shocked Spain and brought about the legalisation of the Communist Party. She became a senior judge in Madrid in 1993. Her legal brilliance was matched by her management skills, which reduced waiting lists for hearings from two years to a matter of weeks and did away with a system of queue-jumping, based on favours and corruption, that had been in place for centuries. Carmena’s many enemies – she acquired more in the recent elections – argue that to run Madrid efficiently, conviction and a penchant for anti-corruption are not enough.

Thirty years younger, Ada Colau made her mark when she challenged the country’s mortgage system – the developed world’s most onerous form of indenture – and the ‘criminal’ bankers that run it. In Spain, if you slip into arrears on your mortgage, your bank may evict you and repossess your property without deducting its value from your outstanding debt (which will balloon because annual default interest rates of up to 20 per cent compound fast). If the bank then sells the property and the sale proceeds exceed the loan, it pockets the profit. Death won’t cancel it either. Anachronistic laws in Spain confer unlimited personal liability on the borrower and load the dice in favour of the banks (in the UK personal bankruptcy is an option; in the US you can hand your keys to the bank and start over). The Spanish system creates the perfect conditions for real estate bubbles (banks bear no risk), dampens aggregate demand (slaves to the mortgage spend less) and drives the informal sector, with defaulting mortgage-holders working off the books whenever possible (earnings in the grey economy are invisible to the courts, who can levy arrears from a formal sector paycheck and hand them to the bank).

To publicise her social justice agenda, Colau dressed up as ‘Supervivienda’, a kind of housing Superwoman. In the first five years her Plataforma de Afectados por la Hipoteca (PAH, or Forum for People Hit by Mortgages) had intervened to fend off more than a thousand evictions. The media made the most of Colau’s grassroots symbolic successes and the EU has called for a change in eviction laws, but in Spain nothing has changed.

The ancien régime is nervous. Its attempts to shut the door on newcomer politicians were doomed. In Madrid an eccentric offer by the Popular Party to form a coalition government with the Socialists was quickly rejected. The conservative nationalist incumbent in Barcelona, Xavier Trias – highly efficient, much respected – disappointed his supporters by throwing in the towel: with 10 council members to Colau’s 11 (21 are needed for a majority) he did not fight for an alternative coalition, either with left wing pro-independence parties or with other traditional parties. Yet neither Carmena nor Colau has an outright majority; every time the budget or a big initiative comes up for approval a ‘variable geometry’ deal to reach a majority will have to be negotiated; in this ad hoc system the establishment is bound to have an influential voice.

The challenges of Madrid and Barcelona are not the same. Madrid is the administrative capital, hosting dozens of Spanish corporate headquarters and presiding over a sprawling, underused infrastructure: its ability to invest and spend may now be reaching a limit, given the size of its debt (€6 billion to Barcelona’s €978 million). Barcelona, by contrast, has found a global city-state niche: Colau and her newly appointed head of economic affairs, Jordi Ayala, a Trotskyist, can only tinker on the edges of the dynamic services-driven Mediterranean city. She has already decided to replace the mayoral Audi with a modest Seat Altea, which has won her plaudits. She has also cancelled Barcelona’s bid for the 2026 Winter Olympics, and announced reduced fines for skating, prostitution and playing ball on the streets. But Barça fans are vigilant: if Colau had her way, the FCB’s extravagant plans for a new stadium might come to grief. How would Supervivienda fare in a showdown with the institution that raises passions like no other in the city and which, this year, looks set to become the club with the largest revenues in the world?