WASHINGTON (Reuters) - Former Democratic presidential candidate Hillary Clinton says in her new book that Donald Trump made her skin crawl by stalking her around the stage in a campaign debate and she wonders if she should have told him to “back up, you creep.”

In audio excerpts of the book “What Happened” aired on Wednesday on MSNBC, Clinton described her 2016 campaign as “joyful, humbling, infuriating and just plain baffling” and acknowledged she failed her millions of supporters by losing to Trump in the November election.

In the excerpts, Clinton described the Oct. 9 debate in St. Louis in which Trump followed her closely about the stage, lurking behind her as she fielded questions from a live television audience. The debate came two days after an audiotape emerged in which Trump was heard bragging about groping women.

“This is not OK, I thought,” Clinton says. “It was the second presidential debate and Donald Trump was looming behind me.

“We were on a small stage and no matter where I walked, he followed me closely, staring at me, making faces. It was incredibly uncomfortable. He was literally breathing down my neck. My skin crawled,” Clinton said.

“It was one of those moments where you wish you could hit pause and ask everyone watching: ‘Well, what would you do?’ Do you stay calm, keep smiling and carry on as if he weren’t repeatedly invading your space? Or do you turn, look him in the eye and say loudly and clearly: ‘Back up, you creep. Get away from me. I know you love to intimidate women but you can’t intimidate me.’”

Clinton says she chose the first option.

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“I kept my cool, aided by a lifetime of dealing with difficult men trying to throw me off,” she says.

But Clinton questions whether she should have chosen the second option.

“It certainly would have been better TV,” she says. “Maybe I have over-learned the lesson of staying calm, biting my tongue, digging my fingernails into a clenched fist, smiling all the while, determined to present a composed face to the world.”

Clinton says writing the book, due to be released in the coming weeks, “wasn’t easy.”

“Every day that I was a candidate for president, I knew that millions of people were counting on me and I couldn’t bear the idea of letting them down. But I did,” she says. “I couldn’t get the job done.”