But in the end, costly mistake after mistake after mistake ultimately cost the team a chance at elusive number 15. If any one of those, it seemed, had been corrected, had gone in the Crimson’s favor, then that winning streak might still be alive and well. One fewer dropped pick, one fewer excessive celebration penalty, one fewer this or that, and who knows.

Yes, this was a game that left Harvard fans with more “what ifs” than a Michael Sandel lecture.

And it all came to a head in that fateful fourth quarter, when the Tigers reeled off those 29 unanswered points—more points than Harvard has ever allowed in program in the final frame in program history—and everything unwound in a stunning and epic collapse.

It wasn’t only those mistakes, though, that allowed for such a remarkable comeback. After allowing only 51 passing yards in the first half, the Crimson secondary struggled mightily in the second two quarters. This wasn’t the unit that shut down Cornell’s mighty attack; it wasn’t the group that gave up 23 points in its previous three contests.

After a strong first half, the secondary gave up a whopping 241 passing yards in the second. By comparison, entering the contest, the Tigers averaged just 163 yards through the air each game.

Even worse: In the fourth quarter, Princeton threw four touchdowns. Coming into Saturday’s game, the Tigers had thrown for just three all season long, and Harvard had allowed just five.

But for some reason, once more, Princeton had Harvard’s number. For the two years prior, the otherwise-anemic Tigers offense had put up more points against the Crimson than any other league competitor. And that trend continued on Saturday—a weak Princeton offense shined against Harvard—but this time, unlike the past two years, it was the Tigers who came away with the ‘W’.

And now, after its first loss since early in the 2011 season, the Crimson must deal with another reality: that Ivy League title that seemed so firmly in its grasp for a second straight year is now, all of a sudden, anything but a done deal.

With the Tigers undefeated, the fate of the Crimson—considered even by Princeton’s coach as the top team in the conference—is no longer in its own hands.

—Staff writer Robert S. Samuels can be reached at robertsamuels@college.harvard.edu.