Sisse Marie Welling from the Socialist People’s Party (Socialistisk Folkeparti, SF) will become Copenhagen’s new lord mayor (overborgmester) after a historic cross‑party agreement that ends more than a century of uninterrupted Social Democrat control of City Hall.
A historic break with Social Democrat rule in Copenhagen
For more than 100 years, Social Democrat mayors have led Copenhagen. Since the current system of city government was introduced in the late 1930s, every lord mayor has come from the same party, even as the political map of the capital has shifted over time. The decision to hand the top job to SF’s Sisse Marie Welling therefore marks a rare institutional change as well as a political defeat for the Social Democrats.
The agreement was presented in the early hours of Wednesday at Copenhagen City Hall (Københavns Rådhus), after a night of intensive negotiations between the parties elected on Tuesday 18 November. Standing in front of the assembled press, Welling called the outcome “historic” and underlined that power in the city should never be taken for granted. In her view, it is “healthy” for Copenhagen that political leadership can change hands and that new actors are given the chance to set the agenda.
Outgoing Social Democrat lead candidate Pernille Rosenkrantz-Theil acknowledged the loss, describing it as “fair and square” in a democratic system and calling the result “insanely regrettable” for her party. The shift caps a long downward trend for the Social Democrats in the capital, who have lost support at every municipal election since the mid‑2000s.
A broad coalition behind Sisse Marie Welling
One striking feature of the new arrangement is the breadth of the coalition that has formed around Sisse Marie Welling. Behind the agreement stand Enhedslisten (Red‑Green Alliance), Alternativet, Venstre (the Liberal Party), Det Konservative Folkeparti (the Conservatives), Radikale Venstre (the Social Liberals), Dansk Folkeparti, and Liberal Alliance, alongside SF itself. In total, the parties backing Welling account for a clear majority of the 55 seats in the city council.
The only parties outside the deal are the Social Democrats and Frie Grønne (Independent Greens). According to Welling, the door remained open for the Social Democrats throughout the talks, but they declined to join unless Rosenkrantz-Theil herself became lord mayor. The final constellation therefore reflects both the numerical strength of SF and Enhedslisten on the left and a strategic decision by several centre‑right parties to support a compromise candidate from SF rather than see Copenhagen led by the Social Democrats or by the more radical Red‑Green Alliance.
Welling emphasised that the new majority will try to break with the perception of City Hall as a closed club. By bringing together parties from across the political spectrum, she argues, the coalition can work more pragmatically on issues such as housing, welfare and climate, and avoid the stalemates that have sometimes characterised negotiations in the past.
Election results reshape the left‑green balance
The municipal election in Copenhagen confirmed a strong but fragmented left‑green majority. Enhedslisten remained the largest party in the city with 22.1 percent of the vote, despite losing support compared to 2021. SF made the biggest gains, rising to 17.9 percent, while the Social Democrats fell further to 12.7 percent, their worst result in the capital in modern times.
Among the other parties, the Conservatives finished on 11.3 percent, the Social Liberals on 10.5 percent, Venstre on 6.1 percent, Liberal Alliance on 5.2 percent and Alternativet on 5 percent. Dansk Folkeparti improved its position to 3.8 percent, while smaller lists such as Frie Grønne, Moderaterne and Denmark Democrats remained below two percent. In total, 349,463 votes were cast in Copenhagen, corresponding to a turnout of 65.6 percent.
The numbers explain why the question of the lord mayoralty was wide open on election night. With three sizeable left‑leaning parties and several medium‑sized centrist and conservative lists, no single bloc could claim an obvious mandate to lead the city. By opting for SF’s candidate, the parties have signalled a desire for a green and social agenda that is still seen as compatible with economic pragmatism.
From health mayor to City Hall leader
Before becoming lord mayor, Sisse Marie Welling served for eight years as mayor for health and care (sundheds- og omsorgsborgmester), and she has been a member of the Copenhagen city council (Borgerrepræsentationen) for 15 years. At 39, she represents a relatively young generation of municipal politicians who have built their careers inside City Hall rather than in national politics.
Welling lives on Amager with her husband and two children, and she often links her political priorities to everyday life in the city – from metro commutes to playgrounds and swimming trips at Amager Strand. In her time as health mayor, she worked on strengthening elderly care and public health services, emphasising prevention and the link between social conditions and health outcomes.
Her campaign for the overborgmesterpost framed Copenhagen as a city facing a housing crisis and growing inequality between neighbourhoods. She argued that educators, nurses, students and families with children should still be able to afford to live in the capital, and that public services must keep pace with population growth. For Welling, the task of the new majority is to turn Copenhagen into a “children’s city” with calmer daily routines for families and better conditions for those who work in welfare professions.
What Copenhagen can expect from the new SF mayor
In programme terms, SF in Copenhagen has promised a combination of climate‑focused urban development, stronger welfare services and a clearer social profile in housing policy. That includes more affordable rental housing, efforts to curb speculation in the city’s limited housing stock and investments in green public spaces, trees and urban parks.
On climate and mobility, Welling has signalled continuity with Copenhagen’s existing goals of becoming a carbon‑neutral city, but with more emphasis on liveability. This includes safer routes for cyclists and pedestrians, measures to reduce traffic in dense neighbourhoods and further expansion of public transport, alongside new green areas that can absorb heavy rain and mitigate heat in summer.
The broad coalition behind her suggests that Copenhagen politics will continue to be characterised by compromise. Centre‑right parties are likely to focus on business conditions, budget discipline and efficient administration, while the left and green parties will push for ambitious climate targets and redistributive housing policies. Welling’s ability to navigate these tensions will determine whether SF can consolidate its control of the overborgmesterposten beyond a single term.
For now, the symbolic impact is clear. With Sisse Marie Welling as Copenhagen’s first SF lord mayor, the Danish capital becomes a key laboratory for how a green‑left party can lead a major European city – and a visible reminder to the national government that its traditional stronghold is no longer guaranteed.
