DAYTON, Ohio (AP) -- President Barack Obama and British Prime Minister David Cameron saw a huge comeback.
Had they stuck around a little longer, they could have watched the biggest one in NCAA tournament history.
Noah Hartsock scored 16 of his 23 points in the second half and the Cougars came back from 25 points down to beat Iona 78-72 in the first round Tuesday night.
It marked the biggest comeback in an NCAA tournament game, the NCAA said. Previously, the largest deficit overcome was 22 points when Duke fought back to beat Maryland 95-84 in the 2001 national semifinals.
Hartsock was a little hurt that the president wasn't around to see the fireworks in the nightcap.
"I started looking around and didn't see him," Hartsock said with a grin. "But I'm sure he had some important things to take care of."
It was the second incredible turnaround of the night in Dayton. With the two heads of state watching from front-row seats on the baseline, Western Kentucky came back from a 16-point deficit in the final 5 minutes to beat Mississippi Valley State 59-58 in the first game.
That was the biggest margin overcome by a team in the final 5 minutes to win an NCAA tournament game, the NCAA said.
No matter how far they fell behind, BYU and coach Dave Rose had faith that the Cougars could somehow come back.
"Coming back from 25 points down is really satisfying now that we've won. At the time it wasn't that satisfying being down 25," he joked. "But I don't think that any of us, especially the coaching staff or our players, doubted the fact that we could chip into that lead."
Brandon Davies added 18 points and Damarcus Harrison 12 for the 14th-seeded Cougars (26-8), who advanced to play third-seeded Marquette on Thursday in Louisville, Ky.
There was no consolation for Iona.
"It's going to be one that we have to live with the rest of our lives," Gaels coach Tim Cluess said. "It's a tough one we let get away. No excuses."
Iona (25-8) seemed assured of its first official NCAA tournament victory after dominating the first half. But despite 15 points and 10 assists by Scott Machado, the Gaels dropped to 0-8 in NCAA play. Their lone win in 1980 was vacated due to NCAA violations.
Iona came in as the nation's top-scoring team at 83.2 points per game and didn't disappoint - at least in the opening 16 minutes. The Gaels scored 55 points in an eye-popping display of passing wizardry and outside shooting. Then they didn't score over the final 4:30 of the first half.
BYU then took control, slowly but surely. The Cougars held the Gaels without a point for 9:20 in a 17-0 run to narrow the deficit to 62-61 midway through the second half. BYU made up ground with a trapping half-court defense that forced the Gaels out of their hurry-up-and-shoot-3s attack. At the other end, the Cougars were getting buckets from Hartsock on fallaway jumpers.
"We just were more aggressive," Cougars guard Brock Zylstra said. "We were doing to them what they were doing to us in the first half."
Iona scored 55 points in the first 16 minutes, then managed just three field goals and seven points over the next 16 1/2 minutes.
Jermel Jenkins ended the lengthy drought with a 3 from the left corner with 8 minutes left.
From there on, the teams traded baskets as the pace slowed. Machado's three-point play pushed the lead to 70-64 with 5 minutes remaining before Hartsock hit an outside shot. After two missed foul shots by the Gaels, he hit another short turnaround jumper to cut the lead to two.
With 2:26 left, Hartsock popped out on the right wing to hit a go-ahead 3. It was the Cougars' first lead of the game.
"This is a team that's worked hard all year, that's never given up," Hartsock said.
Davies added two free throws in the final minute before Zylstra scored in transition and turned it into a three-point play, and the comeback was complete.
It was a shocking turn of events because of how well the Gaels - who also got 13 points from Jenkins, 12 from Mike Glover and 10 by Sean Armand - started out.
"You're looking for answers out there, looking for guys to make a play," Cluess said. "Their good player is drilling it with guys in his face and guys draped all over him. Big-time players have to make big-time plays."
Rose, a co-captain for the old Phi Slamma Jamma teams at Houston, has tasted disappointment before. But not this night.
During a timeout in the middle of the comeback, he saw something he'll never forget.
"The look in our players' eyes at that time was, `Game on. We've got a chance here,"' Rose said. "And we were able to finish it off."