But where one door closes, another opens. On the same day that Mr. Brown plans to introduce his running mate, Harford County Executive David Craig, a Republican, plans to announce his candidacy for governor. He brings extensive experience in state and local politics, as well as a pragmatic outlook on governance. A number of other Republicans may follow — Del. Ron George, an Annapolis businessman, is expected to announce his candidacy next week, and Frederick County Board of Commissioners President Blaine Young, former U.S. Senate candidate Dan Bongino, Republican activist Charles Lollar, former Ehrlich administration official Larry Hogan and former Lt. Gov. Michael S. Steele are all considered possible candidates.