Warding off some hard history, the Amherst Lord Jeffs defeated Williams yesterday, 26-21, in yet another gut-wrenching installment of “The Biggest Little Game in America.’’

The victory gave the Jeffs their first win over Williams since 2004, their first outright NESCAC championship, and perhaps most important, a perfect 8-0 season - their first unblemished campaign since 1984.

“That was certainly the goal,’’ said coach E.J. Mills, his voice hoarse. “We just kept believing. We just kept getting better.’’

“These guys, this year, we set out on a mission that 5-3 is no more, that losing to Williams is no more,’’ said one of Amherst’s captains, Chris Govey, who said the team’s commitment began as soon as last year’s anguished 24-23 loss to Williams was in the books. “This is what we did it for. It’s an absolute dream come true.’’

Seven times in the last 52 years Amherst’s bid for an undefeated season had been denied in the last game of the year by Williams. The last three times had been particularly excruciating. In 1996, when Mills was Amherst’s defensive coordinator, Williams won in the final minute, 19-13. The next year, Mills’s first as head coach, Williams triumphed in the final two seconds, 48-46. Then in 2001, the Ephs prevailed in overtime, 23-20.

So after Williams had sliced a 26-14 lead to 26-21 in the fourth quarter, and then recovered a fumble in Amherst territory with 3:44 left, it was easy for the Jeffs to see the galloping ghosts.

“You try to stay focused, but the bottom line is that bad stuff starts to creep in a little bit,’’ admitted Mills.

On the other side, the Ephs - even after a game of enormous frustration (three interceptions, a fumble returned for a touchdown, a slew of critical passes falling off fingertips on both sides of the ball) - felt destiny calling once again.

“I honestly thought the game was ours when that happened,’’ said Williams quarterback Patrick Moffitt (19 of 31, 239 yards, two touchdowns, two interceptions). “Everyone was ready to go.’’

The game came down to one play with 1:18 left and Williams facing fourth and 4 from the Amherst 23. First Mills called a timeout. Then Williams coach Mike Whalen called one. And then, with purple-clad fans on both sides standing, Moffitt hit tight end Jon Carroll slanting toward the sideline. He lunged for the first down, but got upended a yard shy on a great tackle by cornerback Fran Florio.

“I think it was our best football play,’’ said Whalen. “I don’t have any regrets about it. You got to take your hat off to them. They made the play. For them to come in here on our field and beat us, they deserve to be undefeated. They really do.’’

Amherst opened the scoring on a 29-yard field goal by Matt Rawson. Williams then seized control as Moffitt hit B.J. Griffin for a 24-yard touchdown, and Bryce Bennett for a 28-yarder and a 14-3 lead early in the second quarter.

The Lord Jeffs responded, though. Alex Vetras (20 of 35, 290 yards, two touchdowns, no interceptions) unloaded a 70-yard scoring strike to Andrew Reed. Then with 4:08 left in the half, a high snap on a would-be punt led to a 33-yard scoop-and-score touchdown for Eric Bunker and a 17-14 halftime lead.

Amherst continued the momentum surge as Rawson connected on a 28-yard field goal late in the third quarter, and Vetras hit Brian Murphy on a tipped pass early in the fourth. The Jeffs seemed to be in control, having scored 23 straight points for a 26-14 lead.

A Moffitt quarterback draw from 4 yards capped a 67-yard drive that cut the gap to 5 points with 10:23 left. That set the stage for the dramatic finish, with Williams coming up just short and settling for a 6-2 season, while their archrivals celebrated all over soggy Weston Field.

“E.J. [Mills] and I are close,’’ said Whalen. “I told him, ‘Undefeated seasons don’t come around too often, so enjoy it.’ ’’