Since the 1856 US presidential election, the Democratic and Republican parties have dominated the popular vote, effectively creating a two-party system. During that time, only three elections (1856, 1860, and 1912) have seen third parties earn more than 20% of the vote. The 1992 election was close, with Ross Perot running as an Independent, earning 18.9% of the vote.

Canadian federal elections have witnessed the opposite trend – from 1867 to 1988, conservative and liberal parties earned more than two-thirds of the popular vote, but have not reached that level in the seven elections since 1993. For Canadian political parties, conservative refers to the following: Conservative Party of Canada, Progressive Conservative Party, Liberal-Conservative Party, Unionist Coalition, National Liberal and Conservative Party, National Government Party and Conservative-Labour. Liberal parties include: Liberal Party of Canada and Anti-Confederates.

Data sources:

http://www.parl.gc.ca/parlinfo/compilations/electionsandridings/ResultsParty.aspx

http://www.electionalmanac.com/ea/canada-popular-vote-results/

http://uselectionatlas.org/RESULTS/