"We've got somebody down," she called to the sidelines of the event.
"Help is on the way!" she shouted, to laughter. She then urged the crowd to "bend your knees," a line both President Obama and the first lady have used to respond to fainting incidents at campaign events, particularly during hot summer months earlier this year.
The president has even attempted preventative instructions, after several past incidents where audience members fainted while he was speaking.
“Make sure to bend your knees because some people faint, fall down," he warned students in Ohio last month. "Not because I’m so exciting, but just because you’ve been standing for a long time."
And the first lady offered an energetic demonstration on Tuesday.
"Here's the trick when you're standing up: You've got to bend those knees," she said, bouncing up and down.
A few minutes later into her speech, the first lady paused to ask, "Do we need water over there? Water!"
It was unclear whether the first lady was speaking to the same member of the crowd, but a few minutes later she acknowledged that the supporter was back on their feet, prompting the crowd to cheer. "Are we up? Up! Alright, now I'm happy."
"It's hard to stay fired up," she added. "I want to make sure everybody's okay."
Between the off-script moments, the first lady jumped seamlessly back into her usual campaign speech, touting her husband's character and accomplishments during his first term as well as urging supporters to vote and make sure neighbors and friends are registered to do the same.
The first lady will also headline a private fundraiser in Virginia on Tuesday night. Recent polling in Virginia shows Obama with a very tight lead over Mitt Romney.