No one can spot a lost cause quicker than a successful politician, so when the boat bearing Sen. Edward M. Kennedy took off from the America's Cup spectator fleet late this afternoon with the yachts still racing, the message was clear.

Liberty was a goner.

He wasn't wrong. Sleek Australia II went on to score the biggest victory by a foreign challenger in modern history with a 3 minute 14 second drubbing of the American defender.

The long-awaited first victory by the trouble-plagued challenger left the score 2-1 in favor of Liberty in the best-of-seven final cup series.

And it left Australian syndicate chief Alan Bond fairly crowing. "This win consolidates the superiority of the team," he said. "I feel great optimism that we have the possibility to win the cup."

The Americans immediately called a lay day Monday in hopes a stiffer breeze comes along to replace the moderate wind in which Australia II excelled today. But what they can do to compensate for the obvious superiority of the challenger in gentle winds and smooth seas is a mystery.

"You can cover up for a lot of things," Courageous skipper John Kolius said a few weeks ago during trials to pick a defender, "but boat speed isn't one of them."

Today the boat speed advantage of Australia II, with her controversial winged keel, was clear before the first leg of the six-leg contest was half over.

"The red boat (Liberty) is parked," said veteran 12-meter sailor Gary Jobson, watching from the press boat. "There is no way she can keep up with the white boat in these conditions."

Liberty skipper Dennis Conner agreed. "She was going higher (closer to the wind) and faster," he said after the race.

Conner managed to cross the starting line first by eight seconds but by the time the boats rounded the first mark 4 1/2 miles upwind Australia II was ahead by 1 minute 14 seconds.

It was very similar to events on Saturday, when Australia II led all around the race course but was denied victory when winds died and the 5 hour 15 minute time limit for completing the race expired.

But today the moderate southwest breeze of seven to 10 knots held steady and there was never danger of abandonment. The start of the race was delayed almost two hours while the race committee waited for the winds to fill.

Conner tried every tactical trick in his arsenal to break the advantage of the white boat, but Australia II skipper John Bertrand, the victim of gear breakdowns and tactical errors in his first two losses, answered every volley in kind.

Conner cut into the lead on the second and third legs, reducing the margin to 52 seconds at the second mark and 42 seconds at the third, but when the boats headed back into the wind for the second time under sunny skies Bertrand worked the advantage back to 1 minute 15 seconds.

In that second 4 1/2-mile upwind leg Conner tacked through the wind 39 times, going back and forth from one side of the course to the other in an apparent effort to wear the other side down. But Bertrand's crew was up to the challenge.

Conner said, "We tried most everything we could think of. She (Australia II) looked awfully good."

It was on the next racing leg that Kennedy, observing from a 28-foot powerboat at the head of the spectator crowd, made his exit. He missed the worst.

Bertrand stretched the lead to 2 minutes 47 seconds at the fifth mark and then added another 27 seconds to his lead as he roared back upwind for the final victory leg.

The Australians fouled up the first two races, breaking a steering pulley to lose the first, then suffering a tear of the mainsail to lose the second.

But today's victory was decisive and record-setting. Challengers have won only three races in cup competition since 12-meter yachts were chosen as competing boats in 1958. The widest previous margin was 1:02, by Gretel II over Intrepid in 1970.

Of deep concern to Americans, who have successfully withstood 24 cup challenges since 1851, is the implication of today's win. Australia II compiled a 48-6 record in summer-long trials to pick the challenger, and her margins over the other six contenders were often three minutes or more.

The Americans hoped that indicated a poor level of competition, but today the same fate befell them.

The mustachioed, 37-year-old Bertrand said his crew won't celebrate. "What we've done is get back in the ballpark," he said in a characteristic soft voice. "You'll see a very level-headed group tonight. There's no way we want to blow it now."

Conner said he has no tricks up his sleeve. "There's not a whole lot left we can do except hope for wind."

How much wind?

"About 40 knots," said Conner, and managed a troubled smile.