The first lady, no stranger to recycling an outfit, opted for a Michael Kors dress she had worn twice before.
"Kors is pleased to announce that the First Lady, Michelle Obama, wore a Michael Kors magenta silk chine pintucked dress," the designer said in a press release to ABCNews.com.
She paired it with her other fashion staple - a black cardigan.
An Obama source told People that she chose the dress because, "she was so busy with the campaign and their kids that she had no time to think about an outfit and decided at the last minute."
According to USA Today she previously wore the design during a Medal of Honor ceremony in Washington on Nov. 16, 2010, adding a pin to the black shrug. (She wore a House of Lavande Vintage brooch Tuesday night.) She also wore the dress in 2009, sans sweater, for a dressier look.
Fashion writers were calling her choice more restrained than the memorable black and red Narciso Rodriguez sheath she wore for her husband's first victory in 2008 - what many consider her fashion debut.
The New York Times' Cathy Horn tweeted, "Michelle's dress more subdued than one in 2008, but cardie continues!"
The Daily Beast's Isabel Wilkinson wrote, "The new Michelle is all about restraint. … It was an understated, economical choice at the culmination of a campaign that, for the first lady, has been about just that."
As for the Obama girls, they may have come into their own fashion, choosing contrasting brightly colored knee-length flouncy skirts - a departure from their color-coordinated outfits in 2008.
The Times' Horn approved. "The Obama girls might be the fashion news tonight-full skirts, bright color, cute," she tweeted.