In its latest credit update, Fitch rated Fannie Mae’s and Freddie Mac’s subordinated debt and preferred stock ‘AA.’ But the rating service qualified those ratings. “We believe that the U.S. Government’s commitment to residential housing…remains strong. However, we would consider a departure by the U.S. Government from this commitment and/or an adverse alteration to the GSE status to be a material weakening in [their] overall credit profile,” Fitch writes.