Carter called Bell and told his fellow Georgian to "hurry up" on replacing Marston. The administration chose Peter F. Vaira, Jr., an Illinois native, as Marston's successor. Marston prosecuted without regard to party. His targets included the former Republican chairman of Chester County as well as Eilberg, U.S. Representative Daniel Flood, and two powerful Democratic state legislators. After his dismissal as U.S. attorney, Marston ran unsuccessfully in the 1978 Republican gubernatorial primary. He finished in fourth place with 161,813 votes (16.2 percent). The nomination went to Richard "Dick" Thornburgh with 325,376 ballots (32.6 percent). Future U.S. Senator Arlen Specter finished in second place with 206,802 (20.7 percent). Thornburgh as the Republican nominee went on to win the governorship in the fall election. He later served as attorney general in the administration of President George H.W. Bush. In 1979, Marston ran unsuccessfully for mayor of Philadelphia, having been defeated in the heavily Democratic city by William Joseph Green, III. Marston polled 174,083 votes (29.2 percent). Green prevailed with 313,345 (52.6 percent). Another 108,447 (18.2 percent) went to the Consumer Party nominee, Lucien E. Blackwell. After his two political campaigns, Marston established his own law practice. In 1985, he joined the firm Buchanan Ingersoll. There he was a partner with Peter Vaira, his replacement as U.S. Attorney. Marston moved to the Reed Smith firm in 1995. In 2002, Marston left Reed Smith to write a novel about the legal profession. The book was never completed, and in 2005, he joined the firm of Gibbons, Del Deo, Dolan, Griffinger & Vecchione of Newark, New Jersey. He was assigned to open a Philadelphia office for the group. Marston has written numerous nonfiction works over the years. One of his most provocative is "Malice-Aforethought: How Lawyers Use Our Rules to Get Rich, Get Sex, Get Even, and Get Away With It", an attack on the lack of ethics of the legal profession. With former Federal Bureau of Investigation agent Neil J. Welch, Marston co-authored "Inside Hoover's FBI", which claims that organized crime came into existence with the rise of J. Edgar Hoover as the agency director. Marston has a son, David W. Marston, Jr. (born ca. 1970), a Philadelphia attorney with the firm Morgan Lewis & Bockius.