No boat has ever rallied from a 3-0 deficit, although this is the first best-of-nine series in the event's 144-year history.
The only consolation for Conner's team was that the loss was by only 1 minute, 51 seconds - the closest decision yet.
"It was a boat-speed day, and the faster boat won," said Conner, who is two losses away from becoming the first man to lose the America's Cup twice. In 1983, he had a 3-1 lead before Australia II won the last three races.
After yesterday's loss, Conner said he hoped the forecast for tomorrow's fourth race would call for light and shifty winds and choppy seas. Cayard said he wants breezes of 17 knots and smooth seas. John Marshall, the head of the syndicate that lent Young America to Conner, said the boat is at its best in medium conditions.
Yesterday's conditions were medium - and Team New Zealand's Black Magic 1 led at every mark and widened its lead on five of the six legs.
"These races have been tough on our guys," said Young America sail trimmer Bill Trenkle. "We're not used to these kinds of stompings. One thing is clear, they're sailing faster than we are."
Yesterday's win was Team New Zealand's 40th on the water since the challenger trials began Jan. 14. It has lost only once.
To win, Conner must beat the Kiwis in five of the next six races.
"We think our boat is going very well," said Brad Butterworth, tactician for Black Magic 1.