Story highlights Clinton's book is titled "What Happened"

In it, she reflects on the 2016 election

(CNN) Hillary Clinton casts Bernie Sanders as an unrealistic over-promiser in her new book, according to excerpts posted by a group of Clinton supporters.

She said that his attacks against her during the primary caused "lasting damage" and paved the way for "(Donald) Trump's 'Crooked Hillary' campaign."

Clinton, in a book that will be released September 12 entitled "What Happened," said Sanders "had to resort to innuendo and impugning my character" because the two Democrats "agreed on so much."

"President Obama urged me to grit my teeth and lay off Bernie as much as I could. I felt like I was in a straitjacket." - HRC pic.twitter.com/AAaKCq9DAR — Hillary Warned Us (@HillaryWarnedUs) September 4, 2017

The excerpts represent a small number of the roughly 500-page book in which Clinton reflects on her stunning loss to Donald Trump in 2016. The few pages on Sanders are also remarkably candid for a candidate who was more known for being careful than blunt, especially when it came to the Vermont senator.

A Clinton spokesman declined to comment on the published excerpts.

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