in October 2016. On 22 March 2015, the incumbent mayor of Milan,
Giuliano Pisapia, announced that he had chosen not to run for re-election in 2016 for a second term in office. Following Pisapia's decision, the ruling center-left coalition decided to call an open primary election to choose a new single mayoral candidate. Sala and three other people registered to be candidates in this election. The other candidates were Francesca Balzani, the then deputy mayor of Milan, responsible for the Budget in
Milan's municipal government and a former
Member of the European Parliament; Pierfrancesco Majorino, then responsible for Social Equalities in the municipal government of Milan; and Antonio Iannetta, the former president of UISP. The election took place on 6–7 February 2016 and Sala won with 25,600 and 42.3% of the vote. On 5 June, in the first round of the
municipal election Sala gained 41.7% of first votes; on 19 June, in the second round, he defeated the centre-right candidate
Stefano Parisi with 51.7% against 48.3%. On 16 December 2016, Sala suspended himself from office after learning that he was named in an investigation regarding the Expo 2015. He then retired that suspension a few days later. On 7 December 2020, he chose to run for re-election
in 2021. On 11 March 2021, Sala joined the
European Green Party, after years of political independence in the centre-left area. Sala won in October 2021 a second term with almost 60% of the total popular vote. ==Other activities==