DAYTON, Ohio — When Lamar trailed by double digits in the second half of its NCAA first-round game on Wednesday night, there was a lingering feeling that the Cardinals had Vermont right where they wanted them.

Leads were poison on the first night of the First Four at the University of Dayton.

But on the second night, early advantages lasted and the incredible comebacks were muted.

Cool-headed, hot-handed freshman Four McGlynn, who topped the Catamounts with 18 points, led the way in a 13-0 first-half run that gave Vermont a lead that it never let slip away in a 71-59 victory over Lamar.

In the nightcap, South Florida’s nasty defense flirted with perfection in paving the way to a stunning 36-13 halftime lead — yes, you read that right, 36-13 — before cruising to a 65-54 win.

The first two games of the tournament, however, were nightmares for teams in front.

With President Barack Obama and British Prime Minister David Cameron watching from the front row, Mississippi Valley State blew a 16-point lead with 5:07 left in falling to Western Kentucky, 59-58.

It was the biggest comeback ever in the final 5 minutes of an NCAA tournament game.

Then Obama and the Cameron left, barely missing out on the biggest comeback in NCAA tournament history.

Iona scored 55 points in the first 16 minutes and built a 25-point lead only to lose to BYU, 78-72, in Tuesday’s nightcap.

But apparently those incredible turnarounds had only a 24-hour shelf life. The win by Vermont (24-11) sends it into a game with top-seed North Carolina Friday in Greensboro.