A member of the legislative assembly of Lower Canada (1830–37), he opposed Papineau’s Rebellion and was not in sympathy with Mackenzie’s Rebellion of 1837. An outspoken advocate of nationalism, he was arrested in 1838, but soon released, and, after the union of Upper and Lower Canada (1841), assumed political leadership of the French‐Canadian reformers. In partnership with Robert Baldwin he twice formed the government of United Canada (1842–43, 1848–51), on the second occasion serving as Prime Minister in an administration which was notable for its reforms and its achievement of full parliamentary (“responsible”) government in Canada. He left politics in 1851.