Christopherson became chairman of Hamilton's licensing committee, and made a concerted effort to reform the city's notorious regulatory practices.

[6] Christopherson was respected by all parties for his legislative work ethic and contributions to the Standing Committee on Finance and Economic Affairs, and was widely considered as one of the most skilled backbenchers in the government caucus.

The Correctional Services ministry had previously been damaged by reports of sexual abuse and intimidation involving staff at Ontario jails and training centres, and Christopherson was required to enact substantial internal reforms.

[8] He supported former NDP leader Stephen Lewis's recommendations on race relations in the criminal justice system, and made efforts to address racism in Ontario prisons.

[10] This was also a difficult portfolio, and Christopherson has since acknowledged that relations between the Rae government and Ontario police services were extremely tense when he entered the ministry.

Julian Fantino, then an executive member of the Ontario Association of Chiefs of Police, commented that there was "marked improvement" in relations following Christopherson's appointment.

[13] Christopherson also introduced new guidelines for targeting hate crimes, and mandated stricter standards for police investigations of spousal assault.

[17] In addition to his official cabinet portfolios, Christopherson was also responsible for articulating the Rae government's strategy for the proposed Red Hill Creek Expressway in Hamilton.

Although he had previously opposed the project for environmental and other reasons, Christopherson argued in 1994 that a scaled-back four-lane highway would be the "best possible compromise" under the circumstances.

Progressive Conservative Bob Runciman credited him for his competence and managerial skills, while Liberal Tim Murphy described him as "the best of a bad bunch".

Toronto Star journalist Thomas Walkom indicated that he would be a powerful candidate on the centrist wing of the party, and would likely win the support of pro-Rae trade unions such as the Steelworkers.

[26] He continued to serve as his party's critic for Consumer and Business Services and the Management Board of Cabinet, and was a deputy speaker in the legislature from 2001 to 2003.

He promised to reform the city's disclosure laws, requiring municipal politicians to declare their assets, debts and holdings.

[29] Christopherson returned to political life a few months later, defeating Liberal cabinet minister Stan Keyes to win the Hamilton Centre riding in the 2004 federal election.

The Liberal Party won a minority government, and Christopherson served as NDP critic for cities, community infrastructure, labour and steel policy in the 38th parliament.

After the 2015 federal election, Christopherson was appointed as the NDP's critic for the Planning and Priorities Committee and for Public Safety and Emergency Preparedness.

On July 5, 2018, Christopherson announced his plan to retire[34] at the end of the 42nd Canadian Parliament, and to not seek re-election in the 2019 federal election.