Left-wing union of the Labour Party and the GreenLeft. Union concept was put forward by the leader of the Labour Party from January 2021 until April 2022 and former MP Lilianne Ploumen. Union decided to participate in a single contest for seats on the Provincial Council of Zeeland in 2023 as an experiment to 'test the waters' for a national effort ahead of elections for the House of Representatives. Its success after provincial elections held on March 15, 2023 (as a combination, the union became the 2nd largest after the Farmer–Citizen Movement) convinced the union to form a Senate group ahead of Senate elections on May 30, 2023. Union is co-chaired by GroenLinks leader Jesse Klaver and Labour leader Attje Kuiken [Partij van de Arbeid – GroenLinks (PvdA–GL); Labour Party – GreenLeft].
