Marín became mayor Celestino Corbacho's first deputy in 2007. When he resigned the following year to become Minister of Work and Immigration, she was elected as his successor, with 18 votes out of 25. She became L'Hospitalet de Llobregat's third mayor since the Spanish transition to democracy, and the first woman in the office.[1]
The PSC under Marín fell further to 11 of 27 seats in the 2015 Spanish local elections. In November that year, she formed a pact with two independent councillors elected as members of Guanyem Catalunya, still one short of a majority.[4]
In 2017, following the presentation of the unrecognised Catalan declaration of independence, Marín called for Carles Puigdemont, the President of the Government of Catalonia, to confirm that he was not seeking secession, as to avoid the application of Article 155 of the Constitution of Spain being triggered. She reiterated the PSC's support for dialogue and federalism, and praised international businesses for moving their operations from Catalonia in anticipation of secession: "Businesses generate wealth. 500 companies moving is very bad news. If many businesses had reacted earlier, perhaps we wouldn't have got to this point".[5]
In the 2019 Spanish local elections, Marín recovered the majority in the city hall that her party had lost eight years earlier, by increasing their seats from 11 to 14 out of 27.[6]
Marín was arrested and bailed in December 2020 for alleged diversion of funds.[7] The case against her was closed in July 2022.[8] In the 2023 Spanish local elections, her party was the most voted in each neighbourhood of L'Hospitalet de Llobregat, but nonetheless lost its majority.[9]
On 22 May 2024, Marín announced that she would leave the mayor's office on 15 June. David Quirós would become the next mayor.[10]
Other offices
In 2011, she was elected to the Provincial Deputation of Barcelona, and resigned in December 2014 to concentrate on her role as mayor.[11] In July 2019, she was invested as President of the Provincial Deputation, with the deputies from her party and Together for Catalonia voting in favour.[12] That November, she was elected President of the Serra de Collserola Natural Park consortium.[13]
Marín left the Provincial Deputation in 2023 to be named Senator by the Parliament of Catalonia.[16] In September 2024, Illa named her as the Catalan government's delegate to Madrid.[17]