Bryan Clay held a commanding lead through eight events Friday and was on the brink of becoming the first American since 1996 to win the Olympic decathlon gold medal as the "world's greatest athlete."
Clay had 7,365 points with only Friday night's javelin and 1,500 meters remaining.
He was 316 points ahead of his nearest competitor, Andrei Krauchanka of Belarus, who had 7,049. Alexander Pogorelov of Russia was third with 6,979.
The last U.S. gold medalist in the event was Dan O'Brien in Atlanta in 1996.
In his three events during Friday's daytime session, Clay was second-fastest in the 110 meter hurdles (13.93 seconds), set an Olympic best in the discus at 53.79 meters, then cleared 5.00 meters in the pole vault, tied for second-best in the competition.
Trey Hardee, runner-up to Clay at this year's U.S. trials, was a close fourth through seven events but failed to clear his opening height in the pole vault to plummet in the standings.
He missed three times at 4.70, spoiling a chance for the United States to win two medals in the decathlon for the first time since Milt Campbell and Rafer Johnson went 1-2 at the 1956 Melbourne Games. Hardee had cleared 5.00 this year and has a lifetime best of 5.10.
World record holder Roman Sebrle of the Czech Republic, the reigning world and Olympic champion, was seventh with 6,823.
Blue sky replaced Thursday morning's downpour and Clay got off to a fast start, just as he did the day before.
The 2004 Olympic silver medalist and 2005 world champion won his heat in the 110-meter hurdles in 13.93 seconds, well off his best but still the second-fastest time in the competition.
Then came the discus, where Clay dominated as expected. Even though he is small by decathlete standards at 1.80-meters (5-foot-11), 84 kilograms (185 pounds), the throws are among his best events. He set a personal best in the shot put on Thursday.
Clay has led the decathlon leader since winning the first event (100 meters) in a driving rain Thursday.
He knew his first and best discus attempt was a good one, even as it left his hands. He raised both arms as he watched his throw sail well past the 50-meter line. The throw easily outdistanced the Olympic mark of 51.65 set by Dmitriy Karpov of Kazahkstan in Athens four years ago.
The 91,000-seat Bird's Nest stadium was more than half full through most of the morning even though the only competition fans saw was the start and finish of the 50-kilometer walk and three events in the decathlon.