They waited to hear names called out, drawn at random for a coveted seat in Magness Arena.
"I'm really excited. I didn't think I would get to go," said graduate student Catherine Orsborne, who couldn't resist constantly checking her smartphone for new email.
"That's the only way I have written confirmation that I got a ticket."
"You cross your fingers and hope something news-making happens and you tell your grandkids when you're 70 years old I was there," said freshman James Bridges, who also won a seat. "I'm going to be right there as history is happening, but so is everyone else. They're just going to be sitting in their living rooms."
"Maybe they'll see the back of my head," he joked.
As of Monday, there was no official number of seats available for people inside the arena, which is usually home to hockey games.
The debate is a much bigger show, expected to be watched by hundreds of millions of viewers around the planet.
And crews had to make a lot of last-minute adjustments.
"We just realized this morning that there are some rows of seats that we can't put people in because we had to have equipment there," said Peter Eyre who is an adviser to the Commission on Presidential Debates. "It really is a very dynamic process. We've never done a debate here before.
He says all of the entities that get tickets knew that from the beginning.
"We start with the understanding that whatever the final number [of seats] is will be divided up among campaigns and students and the school and those that have made the debate possible," said Eyre. "In terms of precise numbers at this point no one knows that."
What we do know is that this will be a huge moment in the history of the University and a huge moment for Colorado.
DU Chancellor Robert Coombe says the spotlight on his campus is expected to help raise the institution's profile.
He sees the debate as a way to strengthen DU as a "talent magnet," attracting bright people to Colorado.
The University isn't officially considering whether it may try to host another debate in the future, as other institutions have done.
"It's like having a baby," said one official with the University. "We'll have this one and we can decide later whether to have another four years from now."
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