Complex sentence: The racially charged atmosphere was heightened with the arrival in Destrehan of David Duke, who was emerging as a leader in the Ku Klux Klan and neo-Nazi politics in the United States.
Split into simpler sentences: The racially charged atmosphere was heightened by the arrival of David Duke in Destrehan. He was emerging as a leader in the Ku Klux Klan and neo-Nazi politics in the United States.