Complex sentence: The second most popular party was the Libéral (with 14.1%), they were first in the canton-wide election, while the third most popular party was the Les Socialistes (with 13.8%), they were fourth in the canton-wide election.
Split into simpler sentences: The second most popular party was the Libéral (with 14.1%). They were first in the canton-wide election, while the third most popular party was the Les Socialistes (with 13.8%), fourth in the canton-wide election.