The Ethicurean blog and Kim Severson's blog at the New York Times highlight candidates proposed by the sustainable agriculture community. From the Ethicurean's report (and photograph):
Gus Schumacher, Former Under Secretary of Agriculture for Farm and Foreign Agricultural Services at the U.S. Department of Agriculture, Former Massachusetts Commissioner of Agriculture. Chuck Hassebrook, Executive Director, Center for Rural Affairs, Lyons, NE. Sarah Vogel, former two-term Commissioner of Agriculture for the State of North Dakota, attorney, Bismarck, ND. Fred Kirschenmann, organic farmer, Distinguished Fellow, Leopold Center for Sustainable Agriculture, Ames, IA and President, Stone Barns Center for Food and Agriculture, Pocantico Hills, NY. Mark Ritchie, current Minnesota Secretary of State, former policy analyst in Minnesota’s Department of Agriculture, cofounder of the Institute for Agriculture and Trade Policy. Neil Hamilton, attorney, Dwight D. Opperman Chair of Law and Professor of Law and Director, Agricultural Law Center, Drake University, Des Moines, IA.
(Photos of the six are arranged above in order of this list)