Christine Varney‘s July 6 announcement that she’ll soon leave the U.S. Justice Department’s top antitrust post is setting off a swirl of speculation about who will succeed her. Among antitrust lawyers, the early money is on one of two possibilities: an outsider, in Arnold & Porter antitrust head William Baer, and an insider, in Varney’s principal deputy, Sharis Pozen.

The search is sure to get attention because of its enormous impact on the nation’s biggest companies, including AT&T Inc. with its pending $39 billion deal with T-Mobile USA. Baer is a former director of the Federal Trade Commission’s competition bureau, while Pozen, a former antitrust partner at what’s now Hogan Lovells, has been at DOJ since February 2009. Other names lawyers are mentioning: Harvard Law School professor Einer Elhauge, Wilmer Cutler Pickering Hale and Dorr partner William Kolasky and former Simpson Thacher & Bartlett partner Joseph Wayland, who joined Varney’s staff last year.