LONDON (Reuters) - All eyes will be on the swimming pool later on Tuesday when Michael Phelps could make history by becoming the most decorated Olympian of all time and the first man to win the same event on three occasions.
If he succeeds, however, his achievement faces being overshadowed by Chinese sensation Ye Shiwen, 16, who is chasing a second London Games gold medal after setting tongues wagging with an eye-popping swim for her first.
China are top of the medals table on nine golds with the United States second on five.
For the host nation golds are proving elusive but a bronze in the men's team gymnastics on Monday felt almost as good as it ended a 100-year wait for any kind of a medal in the event.
The focus of home attention will be on Wimbledon on Tuesday as Andy Murray competes in the second round, once again carrying the hopes of British tennis fans yearning for a title after his final defeat to Roger Federer in the grand slam tournament there earlier this month.
Women's soccer throws up a tasty tie between North Korea and the United States, at Manchester United's Old Trafford ground, that may prove as much of a spectacle for students of history as for die-hard sports fans as the hermit state and the superpower vie for bragging rights.
Phelps, who wrote himself into the record books in Beijing four years ago by winning eight golds, more than any Olympian in a single Games, is looking for yet more glory.
If the American wins the 200 meters butterfly on Tuesday he will become the first male swimmer to win gold in the same individual event at three successive Olympics - he also landed the title in Athens in 2004.
"I made my first Olympic team in this. The shorter races are a lot better for me now that I'm older," Phelps said of the event that is one of the most physically demanding disciplines in swimming but is also his favorite.
If he goes on to help title favorites the United States to 4x200 freestyle gold later in the day, it would take his overall Olympic medal tally to 19, one more than the all-time record held by Soviet gymnast Larisa Latynina.
Teenager Ye could become the first female swimmer to capture two golds in London when she lines up for the 200 individual medley final after having won the 400 medley on Saturday.
Although there is no suggestion Ye used performance-enhancing drugs - the International Olympic Committee's medical chief said that even raising the issue ruined the charm of sport - she has already issued a quick and firm denial that she cheated.
"There is absolutely no problem with doping," she told reporters through a translator on Monday. "The Chinese team has always had a firm policy about anti-doping."
There was high drama in the pool on Monday too.
Lithuanian swimmer Ruta Meilutyte, 15, struck gold in the women's 100 breaststroke to cap a thrilling day as Frenchman Yannick Agnel also beat American favorite Ryan Lochte in the men's 200 freestyle.
In other developments on the third full day of competition in London, Swiss soccer player Michel Morganella was expelled from the Games for posting an abusive message on Twitter after his team's defeat by South Korea.
It followed the exclusion last week, before the Olympics got underway, of Greek triple jumper Paraskevi Papachristou for another tweet deemed racist at the first Games where social media has become a major issue.
A row over empty seats across London also rumbled on, with organizers under pressure to fill arenas and placate a public furious at seeing TV pictures of unused places having been told months ago that venues had sold out.
British Prime Minister David Cameron said volunteers, soldiers and the public would be able to take some of the available places but added: "You'll never have complete eradication of empty seats".
Ticketing confusion also led to the opposite problem - overcrowding - in at least one instance on Monday.
Dozens of angry ticket holders trying to get into the men's 10-metre air rifle competition at the Royal Artillery Barracks were turned away because the venue was too full.
But London's transport system largely defied predictions of gridlock on the first regular working day of the 2012 Games.
Transport bosses expect an extra three million journeys per day on top of the usual 12 million during the Games, an Olympian test for an underground train network that first opened in 1863 during the reign of Queen Victoria.
(Editing by Tony Jimenez)