The following year, he and several other members of the group joined the Socialist Party, which he led to a landslide victory in the 2012 local elections.

[2] As mayor, Tončev supported a petition from the United Regions of Serbia party calling for the political decentralization of the country.

His statement was quickly rebuked by the party leadership, and, following a new round of negotiations, the Socialists remained in government as a junior coalition partner.

[16] The following month, he indicated that he was considering the possibility of resigning from the Socialist Party to start a new left-wing group that would support the rights of the working class.

[19] In November 2017, Tončev was convicted of having engaged in violent behaviour against a Progressive Party activist at a 2014 pre-election rally and sentenced to three months in prison.

In launching an appeal, he protested his innocence, described the charge as politically motivated, and said that his accuser had in fact been responsible for a disturbance of the peace.