Complex sentence: By 1876, Macdonald and the Conservatives had adopted protection as party policy--part of the so-called National Policy, which was widely promoted in speeches at a number of political picnics, held across Ontario during the summer of 1876.
Split into simpler sentences: By 1876, Macdonald and the Conservatives had adopted protection as party policy. This view was widely promoted in speeches at a number of political picnics, held across Ontario during the summer of 1876.