Fenty called Gray a decent person tarnished by his involvement with the failed Sharon Pratt Kelly administration in the early '90s.
Gray said Fenty has gone from being a popular mayor to one rejected by many community groups.
Fenty argued that he's taken bold, if unpopular, steps to cut government spending while promoting economic development.
One sharp exchange came when Fenty strongly backed Schools Chancellor Michelle Rhee and criticized Gray for not saying whether he would keep her or not. Rhee has said she's committed to serving D.C. children, but she has not said she'd work in a Gray administration.
The Democratic primary is Sept. 14.