Complex sentence: It was formed for the 1919 general election and gained 4.1% of the vote and 20 seats in the Chamber of Deputies, while in 1921 it won only 1.7% of the vote and 10 seats.
Split into simpler sentences: It was formed for the 1919 general election and gained 4.1% of the vote and 20 seats in the Chamber of Deputies. By the 1921 election it had declined and won only 1.7% of the vote and 10 seats.