Hillary Clinton says her skin crawled as Donald Trump loomed behind her during the second presidential debate. In an excerpt from her new book “What Happened,” the former Democratic Party nominee admits she’s not sure she handled Trump properly.

“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 so back up,'” Clinton writes in an excerpt released Wednesday morning on MSNBC’s “Morning Joe.”

The second match-up between Clinton and Trump was a charged one. The Oct. 10, 2016 face-off took place days after tape had been released that had Trump bragging to “Access Hollywood” host Billy Bush about grabbing women “by the p—y.” The audio threatened to derail Trump’s White House race as establishment Republicans sought to distance themselves from the GOP standard bearer.

Trump hit back, going on the attack in the hours before the second debate. He hosted a press conference with Kathleen Willey, Juanita Broaddrick, and Paula Jones, all of whom accused Bill Clinton of inappropriate sexual behavior.

Clinton appears to have been haunted by her decision not to have responded more aggressively to Trump’s hulking physical presence as he followed her around the debate stage.

“I chose option A. I kept my cool, aided by a lifetime of dealing with difficult men trying to throw me off,” she writes “I did, however, grip the microphone extra hard.”

“I wonder though whether I should have chosen option B,” she continues. “It certainly would have been better TV. Maybe I have over-learned the lesson of staying calm, biting my tongue, digging my fingernails into a clinched fist, smiling all the while, determined to present a composed face to the world.”

The second clash and, in particular, Trump’s glowering, stalking performance inspired a “Saturday Night Live” parody that found Alec Baldwin’s Trump following Kate McKinnon’s Hillary Clinton around the stage as the them from “Jaws” plays.

“What Happened” promises to be a more revealing political memoir than Clinton’s previous, more anodyne offerings such as “It Takes a Village” and “Hard Choices.” In an introduction, she writes, “Now I’m letting my guard down.” She blames her upset defeat on a combination of Russian interference and former FBI director James Comey’s 11th hour decision to briefly reopen the investigation into her private email server.

The book hits stores on Sept. 12.