Porter began attending Brigham Young University as a recipient of a David O. McKay scholarship and in 1970 interrupted his studies to serve as a full-time missionary for the LDS Church in the German Mission, based in Düsseldorf, at that time in West Germany. He served for the standard two-year period, completing his service as an assistant to the mission president. Upon his honorable release he returned to Brigham Young University.

Porter served in Germany under two mission presidents who were both native Germans holding United States citizenship, Walter H. Kindt and Rudolf K. Poecker, who served as consecutive mission presidents and had served as missionary companions in the immediate postwar period in what became communist East Germany. Kindt and Poecker had both been arrested a number of times by Soviet authorities because of their missionary activities, and Poecker especially had used his time in Russian incarceration to learn the Russian language and tried to teach the doctrines of the church to any Russians he happened upon. The stories that these two men frequently related to the missionaries under their supervision inspired Porter to change his university major to Russian Affairs.

Porter married the former Susan Elizabeth Holland on February 2, 1977 in the Washington D.C. Temple, and they are the parents of four children.

Before attending Harvard University, where he received a doctoral degree in political science emphasizing Russian affairs, Porter spent a summer in the Soviet Union as an exchange student. He has worked for the federal government on the United States Senate Armed Services Committee and as executive director of the U.S. Board for International Broadcasting. He also worked for two years for the Northrop Corporation. Before accepting a professorship at Brigham Young University, he served for three years (1990-93) as the Bradley Senior Research Fellow at the Olin Institute for Strategic Studies at Harvard University. During this period he authored War and the Rise of the State (Simon and Schuster, 1994.)

Porter's church service after his full-time mission and before his call as a general authority included increasingly more responsible callings. In the 1980s, during a period of residence in Munich, West Germany, where he worked for Radio Free Europe/Radio Liberty as a foreign policy specialist, Porter served as the president of the Munich Servicemen's Branch of the LDS Church. He later served as a bishop in Virginia, and after he accepted a position of Associate Professor at Brigham Young University he was also called to serve as a counselor in a student stake presidency at BYU. He was a counselor to Noel B. Reynolds.

Porter was initially called to serve as a Seventy in the Second Quorum in 1995, but in 2003 was released from that responsibility and called to serve on a more permanent basis in the First Quorum of the Seventy.

Porter is the author of several books dealing with politics and religion.

• USSR in Third World Conflicts: Soviet Arms and Diplomacy in Local Wars 1945-1980 (1984)
• Red Armies in Crisis (Csis Significant Issues Series) (1992)
• War and the Rise of the State (1994)
• The King of Kings (2007)