Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.) called former Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE's "I'm with her" slogan "phony," according to a new book.

In "Shattered: Inside Hillary Clinton's Doomed Campaign," The Hill's Amie Parnes and Sidewire's Jonathan Allen write that members of the Clinton campaign reached out to Sanders aides in late September to share a script of an ad they wanted the Vermont senator to record.

In the ad, Sanders would tout Clinton for her education, healthcare and minimum wage proposals.

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And he would talk about how then-Republican nominee Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE was wrong about climate change and the economy.

At the end of the script were the words: "I'm with her."

“It’s so phony!” Sanders said. “I don’t want to say that.”

Sanders did not use the slogan in the ad.

The Clinton campaign eventually decided not to use the ad on television after learning that voters had some doubts about whether the Vermont senator fully supported Clinton.