2 n. — Politics, informal
a nickname for the Conservative Party.
Type: 3. Semantic Change — Although the term was first coined in relation to the Ontario PC Party under William Davis (see meaning 1), Big Blue Machine has generalized, first to refer to the now dissolved Progressive Conservative Party, and then to the Conservative Party that succeeded it. By the late 1980s, the term was being used to refer to the Conservative government of Brian Mulroney (see the 1988 quotation), and more currently, to the Harper government (see the second 2015 quotation).
In some readings, the term suggests the strategists behind election campaigns, and not necessarily the party itself (see the 1994 and the first 2015 quotations).
Images:

Chart 1: Regional Domain Search, 8 Oct. 2013