While campaigning for Hillary Clinton in Charlotte, North Carolina, First Lady Michelle Obama tore into Donald Trump not only for his late-night tweeting but his claims that his poor debate performance was due to microphone issues.

“When it comes to the qualifications that we should demand of our president, to start with we need someone who will take the job seriously,” Obama said Tuesday.

She went on to defend Clinton’s stamina and tenacity and, while never calling the Republican candidate by name, referenced Trump’s claims that his microphone was defective during the debate by repeatedly tapping her microphone as she said of Clinton, “When she gets knocked down, she doesn’t complain, she doesn’t cry foul.”

“We also need someone who is steady and measured because when making life or death, war or peace decisions, a president can’t just pop off or lash out irrationally,” she said. “And I think we can all agree that someone who’s roaming around at 3 a.m. tweeting should not have their fingers on the nuclear codes.”