Story highlights Michelle Obama spoke Thursday about Trump's crude comments caught on tape

"It has shaken me to my core in a way that I couldn't have predicted," Obama said

Cleveland (CNN) Listening to the audio tape last week of Donald Trump telling a chortling interviewer he employed his fame as an excuse to assault women, First Lady Michelle Obama grew incensed.

The man whose political career was born in the racially-tinged conspiracy about her husband's birth was describing in vile terms a penchant for sexual aggression. This was beyond the standard campaign trail rancor, the first lady would say later. It was something more.

With a campaign speech scheduled for the following week in New Hampshire, Democratic sources said the first lady set to work refining and updating a message she'd been seeking to deliver for a long time about Donald Trump's cruel language toward women.

"This is a speech that the first lady has wanted to personally deliver for a long time," said an aide. "It came directly from the first lady."

That address, delivered at a campaign inflection point as woman after woman emerged to accuse Trump of sexual misconduct, evolved into what could be one of the most effective political speeches of the year.

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