Kwinter was the oldest person ever to be an MPP in Ontario, although at his death, Raymond Cho (politician), was seven months shy of surpassing him.

[1] On July 20, 2017, Kwinter announced that he would not be seeking re-election in the upcoming 2018 election and that "the time has come to let the next generation serve, and I look forward to offering my support to our future York Centre Liberal MPP.

Kwinter was elected to the Ontario legislature in the provincial election of 1985 as a Liberal, defeating incumbent Progressive Conservative David Rotenberg and New Democrat city councillor Howard Moscoe in the North York riding of Wilson Heights (which has a large immigrant population and a prominent Orthodox Jewish community; Kwinter was himself Jewish).

Starr, who was head of the National Council of Jewish Women, misused her position by having the organization make political contributions to the riding associations of prominent Liberal MPPs.

[10] The Liberals were upset by the New Democratic Party in the 1990 provincial election, although Kwinter himself was again re-elected without difficulty, although one contender was better known as the alter-ego of Ed the Sock.

[11] Kwinter faced a more serious challenge in the 1995 election, which was won by the Progressive Conservatives; Tory candidate Sam Pasternak came within 3,000 votes of upsetting him.

Kwinter was challenged for the Liberal nomination in the new riding of York Centre by fellow MPP Anna-Marie Castrilli, who had unsuccessfully competed for the party's leadership in 1996.

Kwinter was subjected to a number of incidents of anti-Semitic abuse during this period, and on one occasion received hate mail at his legislative office.

Kwinter's nomination difficulties proved to be his only real challenge of the 1999 campaign, and he was again returned by a significant margin in the general election.

In 2002, Kwinter publicly opposed the Liberal Party's position on tax credits for parents who send their children to private and non-Catholic denominational schools.

[15] Kwinter put forward a plan to combat marijuana grow-ops in Ontario that would permit local utilities to cut off electrical power to those in the illegal industry.

[16] Kwinter was re-elected in the 2007 provincial election despite a stronger challenge from the Progressive Conservative Party due to its support for extending funding to Jewish and other religious day schools.