After eight years running City Hall, Barcelona's left-wing mayor, Ada Colau, is eyeing a third mandate on May 28, when Spain votes in local and regional elections whose outcome is unclear. 

A total of 36 million people will cast their ballots to elect local leaders and mayors in 12 of Spain's 17 regions on that day, with the election campaign formally starting on Friday. 

The polls are widely seen as a trial run ahead of a year-end general election, which is expected to be a tight race for the left-wing government of Socialist Prime Minister Pedro Sanchez. 

In Barcelona, where Catalan separatists staged a failed independence bid in 2017, polls put Colau neck-and-neck with her two closest rivals -- Socialist candidate Jaume Collboni and Xavier Trias, a conservative nationalist and her predecessor as Barcelona mayor. 

In 2015, after four years in office, Trias lost his seat to Colau, a former housing rights activist.

She was elected at the head of a citizens' platform backed by the hard-left Podemos, the junior partner in Sanchez's coalition. 

The pair are once again set to face off in the polls but much has changed since 2015 in this city of 1.6 million inhabitants.

During the same elections that year, Madrid also elected another Podemos-backed candidate, Manuela Carmena, as mayor but the city has since swung firmly to the right. 

- Tackling mass tourism -

Colau, who doesn't consider herself a separatist, was re-elected in 2019 thanks to support from ex-French premier Manuel Valls, himself a candidate.

He facilitated her investiture to stop the left-wing pro-independence ERC from governing the city. 

Since 2015, Colau has ruled Spain's second city in a coalition with the Socialists.

But given the shifting alliances between parties, among them ERC and the hardline separatist JxCAT, the outcome of the upcoming election is far from clear. 

This time, Colau is pledging to further her achievements in office, with a campaign highlighting advances in housing and transport.

On her watch, the city has created a network of green bicycle- and pedestrian-friendly routes that have reduced traffic and therefore pollution, although overall levels remain high. 

Central to her policies has been a crackdown on mass tourism. 

Colau has shut illegal tourist apartments and limited the number of hotel beds in a city that hit a peak of 12 million overnight visitors in 2019, municipal figures show. 

"In 2015, we inherited a city... with rampant pollution, unrestrained property speculation and unbridled mass tourism, and the first thing we did was to restore order," the 49-year-old said this week. 

But her critics point to rapidly rising rents in the city and say she has held back Barcelona's international development by dragging her heels over plans to expand its airport. 

Such foot-dragging has not been well received in a city where tourism accounted for 12 percent of its output before the Covid pandemic. 

- State of the streets -

"Barcelona is just beginning to throw off the bad reputation it earned through the city hall's policies which have been suffocating the city's very essence," said Jordi Casas, a senior figure in Catalonia's Foment del Treball business confederation. 

According to the latest municipal opinion poll, the issue which most concerns Barcelona residents is the lack of security, followed by the cleanliness of its streets. 

"The city has become uncomfortable and people have lost their self-respect," Trias, its 76-year-old former mayor, complained this week

When Colau was elected in 2015, "there was a desire for change from the traditional parties" and hope that her party would do things differently, says Toni Aira, an expert in political communication at Barcelona's Pompeu Fabra University.

"In the end, she didn't do things so differently because she took on quite an institutional role, although she has made some changes," he told AFP, saying only the ballot would show whether those changes were enough for voters. 

rs/hmw/ds/gil