Complex sentence: In 1948, Perez headed the Thurmond presidential campaign in Louisiana; and after the failure of the Dixiecrat movement, he unsuccessfully tried to keep the party alive, even as Thurmond returned temporarily to the Democratic Party.
Split into simpler sentences: In 1948, Perez headed the Strom Thurmond presidential campaign in Louisiana, when the candidate headed the Dixiecrat movement. Perez unsuccessfully tried to keep that party alive, even as Thurmond returned temporarily to the Democratic Party.