Complex sentence: He was the Republican candidate for Governor of New York in 1986--during the course of the campaign, he carried a prop--a cardboard cutout of then-incumbent Democratic Gov. Mario Cuomo, which he used to humorous effect--however, Cuomo was re-elected.
Split into simpler sentences: He was the Republican candidate for Governor of New York in 1986. During the course of the campaign, he carried a prop--a cardboard cutout of then-incumbent Democratic Gov. Mario Cuomo, which he used to humorous effect--however, Cuomo was re-elected.