In her new book, “This Fight Is Our Fight,” Senator Elizabeth Warren discusses being pressured by Progressives in the Democratic Party to run for President in 2016, and gives her ultimate reason for refusing.

Ultimately, it was her husband, Bruce Mann, who dissuaded her on the idea.

While her husband was supportive, he was wary that a presidential run would be more intense than her 2012 Senate race against then-incumbent Sen. Scott Brown.

“The Senate thing was bad enough, and running for president would be worse — a lot worse,” he had warned her.

During the 2012 Senate campaign, Brown often referred to Warren as “Professor Warren,” a shot at her Harvard credentials, and targeted her for claiming Native American ancestry during her hiring process. Despite the attacks, Warren won the election by 8 points.

Warren also discusses the pressure she faced to endorse either Clinton or Sanders—pressure she did not bend to.

“I didn’t want to undermine either of our candidates or to short-circuit any part of that debate,” she writes.

Warren’s eventual endorsement of Hillary Clinton came the same day President Obama threw his support behind the former secretary of state.