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.

It marked the biggest comeback in an NCAA tournament game, the organization said. Previously, the largest deficit overcome was 22 points in 2001 when Duke fought back to beat Maryland 95-84 in the national semifinals.

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."

It was the second incredible turnaround of the night in Dayton. With President Barack Obama and British Prime Minister David Cameron watching, Western Kentucky came back from a 16-point deficit in the final 5 minutes to beat Mississippi Valley State 59-58.

That was the biggest margin overcome by a team in the final 5 minutes to win an NCAA tournament game, the organization said.

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."

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.

Machado, averaging just under 10 assists a game, had nine at the break.