Complex sentence: There was also an "Anti-Confederation Party" in New Brunswick led by Albert J. Smith whose coalition of Conservatives and Reformers won the 1865 election but then was soundly defeated in the 1866 election by the Confederation Party led by Peter Mitchell.
Split into simpler sentences: There was also an "Anti-Confederation Party" in New Brunswick led by Albert J. Smith, whose coalition of Conservatives and Reformers won the 1865 election. It was, however, was soundly defeated in the 1866 election by the Confederation Party led by Peter Mitchell.