Los Angeles (12-5-7) won its third straight game for the first time this season, while D.C. United (13-8-4) lost for the first time in three matches.
The Galaxy built a 3-0 lead at halftime. Gordon scored into an empty net at the 1:03 mark for his second goal in three games. Omar Gonzalez scored at the end of Donovan’s corner kick in the 25th minute and Baggio Husidic redirected a cross in the first minute of stoppage time before halftime.
D.C. United pulled within 3-1 in the 58th minute on an own goal by the Galaxy’s Leonardo, but Donovan capped the scoring on a penalty kick in the 75th minute for his third goal in three games.
Washington missed a chance to build on its one-point lead atop the Eastern Conference.