“The average age here is probably around 20-something. And that’s only because I’m here, which brings the average age up, quite a bit,” Obama joked.

A $10 admission fee went to a memorial fund named for Alex Okrent, a campaign staffer in Chicago who died during the campaign.

“Alex was one of you,” Obama said. “This incredibly thoughtful, talented, compassionate, caring young person who decided to get involved because he thought he could make a difference. And tragically, he ended up leaving us while working on the campaign … It was heartbreaking. It reminded us of how precious our time on this earth is.”

Obama for America, White House, administration and Presidential Inaugural Committee staff were invited to the ball, started by Obama and the first lady in 2009.

The president, on stage with Michelle ObamaMichelle LeVaughn Robinson ObamaMichelle Obama shares advice for first-generation college students ‘Outnumbered’ host shares ‘9 Rules’ for success in new book Poll: Republicans view Netflix less favorably MORE, introduced the entertainment, “a couple of people who are pretty good musicians — Lady Gaga and Tony Bennett.”