Edward Blake, who had a seat in both the Canadian House of Commons and the Ontario legislature, resigned as Premier of Ontario in order to run in the 1872 federal election as dual mandates had been abolished. Had the Liberals won the election, he likely would have been offered the position of Prime Minister of Canada. The party had no formal leader as such until 1873 when Alexander Mackenzie was given the title after Blake declined due to ill health. Blake was ill during much of the 1872 campaign, and it was Mackenzie who essentially led the Liberal campaign in Ontario, though not outside of the province.
The 1872 general election was the first to include the Provinces of Manitoba and British Columbia, which had both entered the Dominion after Confederation in 1867. By-elections had been held in both provinces to elect Members of Parliament in the newly created ridings, with Manitoba receiving four seats and British Columbia five.
Note:1 Though identifying themselves as Liberal-Conservatives, these MPs and those identifying as Conservatives were both led by Sir John A. Macdonald (himself a Liberal-Conservative) and sat together in the House of Commons.