Warner ran for the
House of Commons of Canada as a candidate of the federal
New Democratic Party in the elections of the
1972 and
1974, but finished a distant third in the riding of
York—Scarborough on both occasions. In 1975, he was elected to the Ontario legislature in the
1975 provincial election, defeating
Progressive Conservative candidate Brian Harrison by fewer than 1,000 votes in the riding of
Scarborough—Ellesmere. He was re-elected by roughly the same margin in the
1977 provincial election. The Progressive Conservatives under
Bill Davis held a
minority government throughout this period, and Warner served as a member of the opposition. He was defeated by Progressive Conservative candidate
Alan Robinson in the
1981 election, when the Davis government won a majority victory. Warner was re-elected in the
1985 provincial election, defeating Robinson by 219 votes as the Tories were reduced to a precarious minority government under the new leadership of
Frank Miller. The
Liberals under
David Peterson were able to form a minority government with outside support from the NDP, and Warner served as his party's critic for Education and Skills Development over the next two years. He was again defeated in the
1987 provincial election, losing to Liberal
Frank Faubert by 481 votes. The NDP won a majority government in the
1990 provincial election, as Warner defeated Faubert by about 4,500 votes in a rematch from 1987. On November 19, 1990, the house chose their Speaker using a secret ballot system. Previously, the Speaker had been appointed by the government. Warner won the ballot over other candidates including Liberal
Jean Poirier and PC
Norm Sterling. He held this position throughout the Rae government's mandate. His tenure in this office was generally free of controversy, unlike the tenures of his Progressive Conservative successors. The NDP were defeated in the
1995 provincial election, and Warner lost his seat to Progressive Conservative
Marilyn Mushinski by over 5,000 votes. ==After politics==