Alexander Campbell articled with John A. Macdonald and became his partner at law for several years beginning in 1843.
Campbell was elected to the Legislative Council as the representative for Cataraqui (now Kingston and the Islands, Ontario) from 1858 to 1867. From 1864 to 1867, he held a series of government positions, including that of commissioner of Crown lands. As a member of the Great Coalition, he attended the Québec Conference. Although Alexander Campbell was not reputed to be a great politician, he was considered a great organizer and was John A. Macdonald's ideal right-hand man.
After 1867, he no longer ran for election, but held several offices with Conservative governments: postmaster general from 1867 to 1873, 1879-80, 1880-81, and from 1885 to 1887; minister of the Interior in 1873; receiver general in 1878-79; minister of militia in 1880; and minister of justice from 1881 to 1885.
Appointed to the Senate in 1867, Campbell acted as government leader from 1867 to 1873 and from 1878 to 1887, and as leader of the opposition from 1873 to 1878. In 1887, he left the Senate and was appointed lieutenant-governor of Ontario.
Swainson, Donald. "Campbell, Sir Alexander." The 1999 Canadian encyclopedia : world edition. Toronto : McClelland and Stewart, 1998.
Swainson, Donald. "Campbell, Sir Alexander." Dictionnaire biographique du Canada. Vol. XII. Québec : PUL, 1990. P. 164-168.