DES MOINES — Deidre DeJear was poised to make Iowa history Tuesday by becoming the first African American nominated by a major political party for a statewide office by outpolling opponent Jim Mowrer in the Democratic Party’s primary-election race for secretary of state.With 13 percent of precincts reporting, DeJear, 32, of Des Moines, was leading with 58 percent of the ballots cast by Democrats in her first bid at statewide office compared to 41 percent for Mowrer, also 32 and from Des Moines.