Prue became a councillor in East York in 1988. In 1993 he was appointed mayor of the borough. The previous mayor David Johnson resigned when he won a provincial by-election. Rather than pay for the expense of a mayoral campaign, the East York council decided to choose a candidate from amongst themselves. Prue won the position after five ballots. The next year, he was elected mayor in the 1994 municipal election and remained in the position until 1997, when East York and the other component municipalities of Metropolitan Toronto were merged into the single municipality of the city ofToronto. Before the 1998 municipal election, Prue successfully lobbied the provincial government to allot a third council seat for East York to improve its representation on Toronto City Council. Following amalgamation, Prue was elected to represent Ward 32 on Toronto City Council.
Provincial politics
On September 20, 2001 Prue won a by-election to replace retiring NDP MPP Frances Lankin in the Ontario legislature. There was some controversy during the by-election. Liberal candidate Bob Hunter accused the NDP of smearing his reputation. He accused Prue of calling him a pedophile based on a book he wrote in 1988. Pages of the book, which portrayed sexual encounters with young prostitutes, were faxed to journalists during the campaign. Hunter launched a libel lawsuit against Prue and NDP leader Howard Hampton but dropped the suit after the election. Prue won the by-election with 50% of the vote while Hunter received 36%. He was re-elected in 2003, 2007, and 2011, with large pluralities. In 2002 Prue undertook a week-long "welfare diet", trying to live on $12.05 for an entire week to draw attention to the condition of Ontario's poorest residents under the Mike Harris government. In 2004 during a debate over expenses charged by school trustees, Prue said that city councillors could do much of the work of trustees. He appeared to support combining the two roles. In 2007 he supported a push for more accountability for executive compensation packages. In May, 2007, he tabled a private member's bill called the Conrad Black Executive Compensation Abuse Act which sought to have pay packages put to binding shareholder votes. He has also championed affordable housing in Toronto,
2009 leadership convention
On July 18, 2008, Prue announced his intention to seek the leadership of the Ontario NDP at its 2009 leadership convention. At a press conference to announce his bid to replace Howard Hampton as leader of the Ontario NDP party, Prue made remarks on public funding for Catholic schools in Ontario. "The NDP policy is there, it says that we support the dual system," he said. "It is time though, I think, that we take a look at that, but we need to leave that to convention. It cannot be my position or an individual's position... rather it must be a party position and we must have an open and frank debate to get to that point." He insisted he wasn't trying to reopen the debate about religion and schools. Prue received 11.5% of the votes on the first ballot, finishing in fourth place. According to the rules of the contest, as the last place finisher he was dropped off the next ballot. Prue gave his personal endorsement to Gilles Bisson who finished in third place on the first ballot with 23.7% of the weighted vote. After Bisson was eliminated on the next ballot, Prue endorsed Andrea Horwath, who won the leadership on the third ballot with 60.4% over rival Peter Tabuns. Prue reported raising $79,411.74 for his leadership bid, the lowest of the four contestants. His expenses were the second highest at $222,320.94. His reported deficit was $142,909.20, the highest of the four contestants.
Following his defeat in 2014, Prue and his wife decided to sell their house in Toronto in order to fund their retirement in a smaller town, moving to Amherstburg, outside of Windsor, Ontario. After sitting on the town's committee of adjustment, Prue was elected to town council in 2018.
