David Robert Peterson PC OOnt KC (born December 28, 1943) is a Canadian lawyer and former politician who served as the 20th premier of Ontario from 1985 to 1990.

In the early 1930s, Clarence Peterson joined the newly-formed Co-operative Commonwealth Federation and was present at the conference where it adopted the Regina Manifesto.

Looking for work during the Great Depression, he moved to Ontario and in 1936 was living in Toronto, where he found a job as a salesman with Union Carbide.

Despite his inexperience, Peterson nevertheless came within 45 votes of defeating Stuart Smith on the third and final ballot of a delegated convention held on January 25, 1976.

Smith presented an image of an articulate intellectual who some delegates said reminded them of Pierre Trudeau while Peterson came across as similar to then Premier Bill Davis.

In his acceptance speech Peterson said that he would move party to the 'vibrant middle, the radical centre', and stressed economic growth as a way to increase support for social services.

After the expiration of the Liberal-NDP Accord in 1987, the Liberals called another provincial election, and won the second-largest majority government in Ontario's history, taking 95 seats out of 130, at the expense of the NDP and the Progressive Conservatives who dropped to third place in the legislature.

It eliminated "extra billing" by doctors, brought in pay equity provisions, and reformed the province's rent review and labour negotiation laws.

His government also brought in pension reform, expanded housing construction, and resolved a long-standing provincial controversy by honouring the Davis Tories promise to extend full funding to Catholic secondary schools.

[25] Although no-one in Peterson's administration was accused of criminal activity, the scandal eroded public confidence in the integrity of the government.

[23] During the first week of the campaign, then-attorney general Ian Scott, claimed that 'while the voters might be cranky at the moment, they ultimately would hold their noses and re-elect the Liberals.

There was no defining issue behind the campaign, and many believed that Peterson was simply trying to win re-election before the economic downturn reached its worst phase.

Some Liberal cabinet ministers, most notably Greg Sorbara and Jim Bradley, were strongly opposed to the early election call.

Peterson justified the early writ claiming "especially after the failure of the Meech Lake Accord, Ontario faced 'profound changes in this country and the world' and that he needed to protect the province in the event of a national-unity crisis", while denying "that he was being an opportunist and trying to capitalize on polling results that put Liberal support at 50 per cent".

It was soon interrupted without intervention by security or police by Greenpeace activist Gord Perks, who arrived with a briefcase handcuffed to his arm, with a tape recorder inside playing a pre-recorded list of broken Liberal environmental promises.

[30] Disappointed by high expectations as well as perceiving that the PC and NDP parties would not be strong opposition, groups representing various interests (such as teachers, doctors, and environmentalists), came out against Peterson on television, radio, in print, and at Liberal campaign events, despite the Liberals having worked cooperatively with these special interest groups prior to the election call.

[31] The media reported the election call as cynical, and the party appeared desperate when they unexpectedly proposed to cut the provincial sales tax halfway through the campaign.

It did not help that the provincial election campaign was being run in the aftermath of the failed Meech Lake constitutional accord of Brian Mulroney's federal government, with which Peterson had significant media exposure in association with the other first ministers.

Peterson felt that the Liberals’ fading poll numbers "reflected greater anxieties about the world and that the party had failed to successfully communicate his government’s accomplishments"; by contrast the NDP's hastily assembled platform called "Agenda for People" managed to escape heavy scrutiny due to their underdog status.

The Liberal campaign slogan shifted from “Effective leadership for a strong Ontario” to “Warning: An NDP government will be hazardous to your health.” Toronto Sun columnist Michael Bennett summed up the divergent fortunes of the Liberals and NDP as campaign progressed, writing “As Peterson became more strident, Rae assumed an almost statesman-like attitude.

Now he didn’t need it.”[27] On September 6, 1990, the NDP scored one of the greatest upsets in Canadian political history, taking 74 seats for a strong majority government.

Due to the nature of the first-past-the-post system as well as numerous fringe parties contesting this election, one third of NDP seats were won with less than 40 per cent of the vote.

[4] After Martin resigned the party leadership in the wake of the Liberal defeat in the 2006 election, Peterson planned to support former New Brunswick Premier Frank McKenna who chose ultimately not to run.

Peterson then backed Michael Ignatieff, criticizing former political opponent Bob Rae's entry into the race due to the latter's record as provincial premier.

[40] In his legal practice he provides international advice to a wide range of clients about public policy issues and government affairs in Canada.

In 1999, Peterson was at the centre of controversy due to his membership on the board of YBM Magnex, a firm which was discovered to have links to the Russian mafia.

A subsequent investigation by the Ontario Securities Commission found that Peterson's actions met "the legal test of due diligence", but expressed disappointment that he had not shown more leadership on the board.

[41] A 2004 report from The Globe and Mail newspaper noted that Peterson was chastened by this experience, and had become "a cautious and more conscientious director" since that time.