[6] In 2000, Cardy co-founded NDProgress, a pressure group within the NDP that advocated the modernisation of the party's governance structures and was sympathetic to the Third Way.

[4] In writing about the debate within the NDP prior to its 2001 convention between the New Politics Initiative and those such as NDProgress, Cardy wrote "Some want to see the NDP recreated as a mass party based on the ideas of the traditional left, but infused with the energy of the new social movements and the anti-globalization activists.

If I had my choice I would fall firmly into this camp, those who want the party to follow the path laid by social democrats like Gary Doer, Tony Blair and Gerhard Schröder.

[10] At the 2012 New Brunswick New Democratic Party convention, Cardy received an 82 per cent vote of confidence in his leadership from the assembled delegates.

[11] During the 2012 federal NDP leadership race, Cardy backed Thomas Mulcair, and was one of the introductory speakers at his campaign launch.

[12] Former party leader Allison Brewer endorsed the Greens due to the policy positions of Cardy's NDP.

Cardy had been working as leader on a volunteer basis since assuming the position in 2011 and had no legislative salary as he was not a member of the provincial legislature.

[21] Cardy resigned as party leader, as well as resigning his membership of both the federal and New Brunswick NDP,[22] on 1 January 2017, complaining of party infighting which he attributed to "destructive forces" colluding with CUPE New Brunswick, the province's largest public-sector union against his leadership.

[23] Cardy said that he "cannot lead a party where a tiny minority of well-connected members refuse to accept the democratic will of the membership."

[25] In April 2017, Cardy was promoted to the position of chief of staff to the official opposition New Brunswick Progressive Conservative caucus.

His resignation letter offered a more detailed explanation,[32] citing Premier Higgs' behaviour in a series of incidents.

Cardy initially committed to staying on as a Progressive Conservative but was expelled from caucus a day after resigning as minister.

[34] Cardy remained in the legislature as an independent MLA for the rest of his term, while announcing he would not be running as a candidate in the 2024 New Brunswick general election.

Authorities stated that Cardy "behaved in a confrontational manner towards other protesters and did not follow police directions" to leave the area.