Complex sentence: He participated in all televised Republican Party (GOP) debates until January 5,2008; noted for his role in the May 15 South Carolina debate where he discussed his experience with border security.
Split into simpler sentences: He participated in all televised Republican Party (GOP) debates until January 5,2008. He was noted for his role in the May 15 South Carolina debate when he stated his position and experience with the issue of border security.