She was one of five women selected by campaign aides for the event, and after each had spoken, she popped the question.
"I understand the kids are getting on the Obama bandwagon," she said, before saying this was the first time since she was 18 that she didn't know which candidate to support.
"You should vote Democratic," was his reply, after saying he had been doing pretty well "among more experienced voters" as well as younger ones.
Getting back to his challenge, Obama put in something of a good word for his Democratic rival, Hillary Rodham Clinton.
"Myself or Senator Clinton, we're all concerned about creating a better social safety net. ... The truth is the differences between my plans and Senator Clinton's health plans are relatively modest," he said.
Then he pivoted quickly into comparison mode.
He said the biggest difference was he didn't think necessary change could be brought about unless "we can bring people together more effectively."
He said it would be necessary to reach across the political aisle, and "I think I can do that better than Senator Clinton."
Next, he said a lot of problems exist because of the "domination of the lobbyists and special interests. ... That's the reason I don't take PAC money, I don't take money from federally registered lobbyists."
Obama said that was something "I take more seriously that Senator Clinton does," adding that she accepts contributions from lobbyists.
Finally, he said, "I think we need a president who is going to be straight with the American people about how we are going to solve problems."
Moments later the conversation ended, without Obama asking Munninghoff whether she had made up her mind.
Initially, she sounded like she wasn't sure what to do.
But a few hours later, in a telephone interview, she said she intended to vote for him.
It's not just one thing," she said, or one question he answered.
Instead, she said she liked "the atmosphere, the aura, the honesty, the comfort I felt."
