Following the union, he represented Dorchester in the Legislative Assembly of the Province of Canada from 1841 to 1844, as an anti-unionist and member of the French-Canadian Group.

[1] Both his father and grandfather were active in politics, being members of the Legislative Assembly of Lower Canada.

He was an officer in the local Dorchester Regiment of the Lower Canada militia, eventually becoming lieutenant-colonel of the 2nd Battalion.

[4] Taschereau was involved in agricultural and forestry development in the Beauce area, particularly in Linière township.

Antoine-Charles had broad support throughout the riding, including from some English-speaking voters.

Following the rebellion in Lower Canada, and the similar rebellion in 1837 in Upper Canada (now Ontario), the British government decided to merge the two provinces into a single province, as recommended by Lord Durham in the Durham Report.

[11][12][13] Taschereau stood for election in the riding of Dorchester for a seat in the new Legislative Assembly.

His opponent was his own nephew, Joseph-André Taschereau, who was one of the few French-Canadians who tended to support the British provincial government at that time.