Montreal city councillor

Caldwell was elected to council on his third attempt, defeating Blanchard (who was by this time serving as Montreal's interim mayor) for the Hochelaga seat in the 2013 election. Project Montréal became the official opposition on city council after the election, and Caldwell was chosen in early 2014 as his party's critic for citizen services and Space for Life.^[6] He was also appointed to Montreal's Commission sur le schéma d'aménagement et de développement de Montréal (Commission on the Land Use and Development Plan) in the same year.^[7]

In June 2015, Caldwell was appointed as a Project Montréal representative on the Commission sur le développement économique et urbain et l'habitation (Commission on Economic and Urban Development and Housing). He initially received this position on an interim basis, filling in for Peter McQueen, who was then seeking election to the House of Commons of Canada.^[8] Ultimately, however, he served on the committee until the 2017 election.^[9]

During his first term on council, Caldwell fought for the Montreal Botanical Gardens to revert to its previous policy of allowing free access outside of operating hours,^[10] promoted self-service carsharing in Mercier–Hochelaga-Maisonneuve,^[11] took part in the preparation of the borough's éco-quartier environmental plan,^[12] and sought to protect natural areas in Pierrefonds-Ouest against a proposed housing development scheme.^[13] In July 2016, Caldwell and borough mayor Réal Ménard (who were not generally political allies) announced the creation of a new public space in the borough called Le patio culturel.^[14]

Caldwell was elected to a second term on council in the 2017 municipal election, which was won by Projet Montréal. Following the election, new mayor Valérie Plante appointed Caldwell to her executive committee with responsibility for urban planning, transit, and Montreal's office of public consultation.^[15]