Complex sentence: During the midterm elections of 1854-1855, the Republican Party was one of the patchwork of anti-administration parties contesting the election, but they were able to win 13 seats in the House of Representatives for the 34th Congress.
Split into simpler sentences: During the midterm elections of 1854-1855, the Republican Party was one of the patchwork of anti-administration parties contesting the election. Overall, the Republicans won only 13 seats in the House of Representatives for the 34th Congress.