Michelle Obama told a diverse and enthusiastic crowd in Philadelphia on Wednesday that candidates don't change once they become president and that America 'needs an adult in the White House'.

The First Lady never mentioned Republican presidential nominee Donald Trump during the rally at LaSalle University. But there was no question that she was warning voters that candidate Trump would be the same as President Trump.

"The presidency doesn't change who you are, it reveals who you are," she told the cheering crowd.

She referred to several comments Trump made during and after Monday's debate, including his apparent acknowledgment that hes paid no taxes some years. Trump said that makes him 'smart'.

She said the country needs a leader who is steady and measured because when making war-or-peace decisions, 'the president can't just pop off or lash out irrationally. No, we need an adult in the White House, I guarantee you'.

She cast Clinton as a tough, compassionate fighter who doesn't back down and who loves her country.