Perth-Wellington MPP Randy Pettapiece is his parliamentary assistant.
Ernie Hardeman ran Hardeman's feed mill in Salford, then became mayor of the township and warden of Oxford County.
He was chair of the Wardens' Association of Ontario in 1990–91, and served as a Board Member on the Association of Municipalities of Ontario.
Hardeman was elected to the Ontario legislature in the provincial election of 1995 and has been re-elected ever since.
In June, 1999, he became agriculture minister for premier Mike Harris, but was removed in February, 2001, for poor performance.
On February 25, 2003, he returned to cabinet under Ernie Eves in the new position of Associate Minister of Municipal Affairs and Housing, with Responsibility for Rural Affairs.
On June 13, 2005, Hardeman's private members bill, Farm Implements Amendment Act, received third reading and royal assent.
After the 2007 election he was named Deputy House Leader and was then promoted to Chair of the Standing Committee on Government Agencies. He was also the PC critic for Agriculture, Food and Rural Affairs.
On June 16, 2008 Hardeman introduced a private member's bill which allows farmers to post seasonal, directional signage along provincial highways to advertise their Ontario grown produce and direct consumers to the farm.
The bill was supported by many agricultural groups and unanimously passed first, second and third reading. On December 10, 2008, Signage to Promote Ontario Produced Agricultural Products received royal assent and became law.