He was a member of the Legislative Assembly of Ontario who represented the ridings of Oriole and Don Valley East from 1997 to 2011 and a cabinet minister in the government of Liberal Premier Dalton McGuinty from 2003 to 2009.
He worked as a commercial real estate agent with the firm of Ernest Goodman Ltd. from 1985 to 1989, and was vice-president of Taurus Metal Trading Ltd. (a recycling company) between 1989 and 1992.
David Caplan contested his mother's former riding of Oriole in the subsequent by-election, and defeated his Progressive Conservative opponent, former federal Member of Parliament Barbara Greene, by a significant margin.
Ontario's electoral map was significantly altered in 1996, when Progressive Conservative Premier Mike Harris introduced a bill to reduce the number of members in the legislature from 130 to 103.
As a result, Caplan was forced to face another incumbent Member of Provincial Parliament (MPP), Minister of Education David Johnson, in the new riding of Don Valley East.
There are several public school teachers in Don Valley East, and many suspect that "strategic voting" by this group against the Tories was a leading factor in Caplan's victory.
He did not, however, join with several other politicians from this community (including fellow Liberal MPP Monte Kwinter) to support provincial funding for non-Catholic religious schools in 2001.
The initiative was brought forward by the Progressive Conservative government of Mike Harris, and the Liberal Party opposed it on the grounds that it would divert money from public schools.
Caplan was easily re-elected in Don Valley East in the provincial election of 2003, defeating his Progressive Conservative opponent, former city councillor Paul Sutherland, by over 9200 votes.
He released a long-term $30 billion plus infrastructure investment strategy called ReNew Ontario, which used a private financing model expanding and building new hospitals, schools, colleges and universities, and transit and transportation systems.
[2] In May 2009, there were opposition calls for Caplan's resignation after it was revealed that eHealth Ontario CEO Sarah Kramer had approved about $4.8 million in no-bid contracts during the first four months of the agency's operation, while also spending $50000 to refurnish her office, and paying consultants up to $300 an hour.