LA Galaxy finally lost after winning four of their previous five matches against D.C. United in the sweltering heat of the RFK Stadium.
As early as the sixth minute D.C. took the lead when Jaime Moreno put away a penalty for his six goal of the season, after Ante Jazic's awkward challenge on Santino Quaranta in the box.
The Galaxy equalised after a comedy of errors when D.C. defenders Devon McTavish and Bryan Namoff collided and fell to the ground, allowing Edson Buddle a simple tap in on 26 minutes.
However, D.C. retained the lead 11 minutes later when Luciano Emilio scored his ninth of the season with a towering header as the first half finished with D.C. in the ascendancy.
As D.C. turned up the pressure in the second half, Marcelo Gallardo put the Eastern Conference side further ahead with a smart finish, beating Galaxy 'keeper Sean Franklin in the box and burying the ball in the back of the net.
The game was effectively put out of the Galaxy's reach eight minutes later when Brazilian Fred cut Franklin out of the game and found Emilio, who rolled the ball into an unguarded goal and finish the game at 4-1.