About 30 people still were standing in two lines when the 90-minute session ended.

One questioner wore a large sign that proclaimed: "America is great because of women, people of color, LGBT people, immigrants, people of diverse religions."

Most of the participants carried cards that allowed them to signal agreement or disagreement with an answer by holding them aloft. A few dozen chose to yell.

"Sir," Sasse said to one man in a red sweatshirt, "you keep shouting, but shouting doesn't help."

Sasse said he does not believe the United States spends too much on national defense and he believes the country "needs better vetting systems" to protect itself from would-be terrorists.

"The United States is not at war with Islam," he said, "but with people who would kill in the name of religion."

Sasse said entitlement reform should protect benefits for people who are retired or within 10 years of what had been considered to be the retirement age of 65 or so when the programs were instituted.

"He hears us, but I'm not sure he listens to us," Ania Szary-Berkowitz of Lincoln said following the event.