As millions of Americans tuned in for the start of this year’s first presidential debate on their televisions Monday, lucky Hofstra University students were already in their seats at the host school’s packed auditorium.

The students — who won tickets to the debate in a lottery system — and other audience members got a behind-the-scenes look at what will likely be a critical moment for both campaigns. But they also were subject to strict rules that set the tone of the event: no clapping or cheering, except at the debate’s beginning and end. Otherwise, the audience was expected to remain silent.

Before the debate got underway, audience members filtering in experienced a little bit more freedom.

Security was surprisingly loose, with guests walking freely, snapping pictures in front of the stage and podiums where the two candidates would stand, said Kyle Gelling, 25, a Hofstra University graduate journalism student.

Once the candidates took the stage and moderator Lester Holt started the debate, the tone became only slightly more serious — though with plenty of interruptions from a very divided audience, students said.

“A comical air was present within the hall from the start,” Gelling said in an email.

“It was like a circus a little bit,” said Ariana Farajollah, 18, a Hofstra freshman from Great Neck who waited nearly two hours to finally get to her seat in the fifth row in the “freezing” auditorium. “There was a lot of whispering. Some people were very outward about it, not even bothering to whisper.”

It was clear that most audience members already knew who they wanted to vote for, she said.

Manmeet Nijjer, 17, a Hofstra student from Cedarhurst, sat in the 10th row at the debate, and also noticed the spirited nature of the audience.

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“There were many times when we were clapping and cheering,” she said. The moderator would hold up his hand to quiet the crowd if an audience reaction lasted more than five seconds, but the rule against audience reaction didn’t seem to be strongly enforced, she added.

Donald Trump’s claim that he will release his tax return if Hillary Clinton releases what he called her “33,000 deleted” emails “was one that got a really big reaction,” she said.

In the debate’s final segment, the crowd became a bit more raucous, with cheers coming every few moments, both for Clinton and Trump. Gelling said the crowd’s disregard for the rules came as people grew tired.

After the debate ended, students saw Clinton leave the stage to greet audience members, but noticed that Trump and his family left the stage without interacting with the audience.

From there, they exited easily to the campus, where the excitement continued.

“News channels are everywhere, so the campus still hasn’t gone to sleep,” Farajollah said, shortly after leaving the debate.