Complex sentence: James R. "Jim" Wilkinson is Managing Partner of Brunswick Group, and has held positions of leadership in the U.S. government, including service as Deputy National Security Advisor for Communications and Chief of Staff of the U.S. Treasury Department.
Split into simpler sentences: James R. "Jim" Wilkinson is Managing Partner of Brunswick Group. He previously held numerous positions of leadership in the U.S. government, including service as Deputy National Security Advisor for Communications and Chief of Staff of the U.S. Treasury Department.