Complex sentence: But in advance of confederation in 1867, the Conservative Party took in a large number of members who defected from the Liberal Party who supported the establishment of a Canadian confederation, becoming the Liberal-Conservative Party until the turn of the twentieth century.
Split into simpler sentences: But in advance of confederation in 1867, the Conservative Party took in a large number of members who defected from the Liberal Party who supported the establishment of a Canadian confederation. Thereafter, the Conservative Party was the "Liberal-Conservative" (in French, "Libéral-Conservateur") Party until the turn of the twentieth century.