In the first semifinal, all three American families cheered unequivocally for Sada Jacobson as the 2004 Olympic bronze medalist rallied from behind to defeat Sofiya Velikaya of Russia, 15-11.
In the other semifinal, however, between two Portland, Oregon, teammates, the family section fell silent between each hard-fought point. Neither the mother, brother, nor boyfriend of Mariel Zagunis, the 2004 Olympic champion, dared say a word, and further down the row, Rebecca Ward's otherwise convivial father, Bill, sat stoically.
"These families are so close," explained David Jacobson. "Out of respect to the others, we're in agreement that families don't cheer and coaches don't coach."
Indeed, Ed Korfanty, who coached both Zagunis and Ward, did not counsel either athlete on-stage during the mid-match break.
"Nobody wants to be the one to knock out an American or be knocked out," Mr. Ward said. "We're happy everyone's in the final four, but there's nothing palatable about it. Their duty [as individual athletes] is to crush the other all they can."
The awkward situation is not new for the US women's sabre fencing team.
"They meet all the time," Mr. Ward said.
The Zagunis-Ward semifinal was, in fact, a rematch of the 2006 World Championship final in which Ward defeated Zagunis to become the first American to win an individual world sabre title.
This time, in Beijing, Zagunis prevailed over Ward, 15-11, and Zagunis' victory set up a gold-medal match with Jacobson.
Afterwards, Cathy Zagunis said, "Now Becca had better win so we can go 1-2-3 like we did in Torino [Italy, at the 2006 Worlds]. The pressure's more on Becca now."
It was Ward's turn to be cheered loudly during her bronze-medal match against Velikaya, and later, the families of the gold-medal contenders would have to self-mute.
It might have been easier had the families separated themselves across the arena. For a while, it appeared that none of them would be granted access to the family box. As they were discussing the night's bouts, an international fencing committee official came over to the group and said that another American family might require the use of that section. The president's father, former president George Bush, was scheduled to arrive for the gold medal match.
Had the fencing families remained where they were, however, their sightline would have been blocked by several large-screen monitors set up for commentators. To remedy the situation, the Jacobsons contemplated pulling the Yale connection, as both Sada and Bush were alumni, but eventually, all the clans were escorted closer to the stage.
In the end, the US team swept the medals and repeated its 2006 World Championship performance, albeit in a different order.
Zagunis won her second consecutive Olympic gold medal; Jacobson upgraded her 2004 bronze to 2008 silver; and Ward, in her Olympic debut, captured the bronze by one point, 15-14.
On Thursday, the three will unite and vie for a team medal together - to the unanimous joy of their entourages.