Trump's remark, in a free-flowing news conference in Miami, steered attention from Philadelphia, where Democrats were preparing Wednesday to hear from Obama, Vice President Joe Biden and Clinton's running mate, Virginia Sen.
Democrats divided over the future of their party agreed on at least one thing as their national convention opened in Philadelphia: Mrs Michelle Obama was a star. Three hours later, the paper tweeted: "Stop the Presses!"
That is the story of this country, the story that has brought me to this stage tonight, the story of generations of people who felt the lash of bondage, the shame of servitude, the sting of segregation, but who kept on striving and hoping and doing what needed to be done so that today I wake up every morning in a house that was built by slaves.
Creative twittering commenced, involving the hashtags #ElectMichelle, #FLOTUSforPOTUS and #Obama2020.
Even Trump, who has an insult ready for any Democrat who crosses his path, had only nice things to say.
Former presidential candidate the Rev. Jesse Jackson Sr. said Obama's speech showed why she is imitated.
"And when I think about the kind of president that I want for my girls and all our children, that's what I want", she added. During her years as first lady, Obama has worn items from Jason Wu to J. Crew in her high-profile appearances.
Their political fates now entwined, President Barack Obama will implore voters Wednesday to elect Hillary Clinton to the White House, appealing to the women, minorities and young people who powered his rise and are now crucial to hers.
The first lady said early on in her husband's tenure, "Politics is important. but it's not who I am and it's never been a goal of mine".
Have you ever seen even a hint of conflict between Michelle and Barack (except for that time he tried to take a selfie at a funeral, because really, wtf?). She was notably silent when Clinton clinched the nomination, letting the historic moment pass without comment. "Based on her ideas and her leadership", Clinton was a better choice than Trump and "must become the next president of the United States", he said.
Tina Tchen, Mrs. Obama's chief of staff, said the two have a "very warm relationship". But there is little evidence of a close friendship.
But her 2016 speech may go down as one of the most memorable of the entire election season.
The base-boosting strategy has some Democrats anxious Clinton is ceding too much ground to her opponent.
For example, Mrs. Obama took on Trump in a June commencement address at the City College of NY, denouncing leaders who engage in "name-calling" and "anger and intolerance". Michelle Obama rejected the partisan political role that Hillary Clinton pioneered in the East Wing, instead embracing the job's ceremonial trappings and family-friendly issues - nutritional standards and benefits for veterans - more common to first ladies.
Ivanka Trump, who has her own fashion line, wore one of her pale pink dresses to introduce her father, Republican presidential nominee Donald Trump, at the Republican National Convention on Thursday night. And for that to happen, Clinton will need the kind of public affirmation from the White House that no one can convey more forcefully than the first lady.
As for talk of political aspirations for the first lady herself, her husband has a big bucket of cold water at the ready.