Warren reveals why she didn't run for president in 2016
© Greg Nash

Massachusetts Senator Elizabeth WarrenElizabeth Ann WarrenSanders endorses Oakland teachers strike On The Money: Dems set Tuesday vote on Trump's emergency declaration | Most Republicans expected to back Trump | Senate plots to avoid fall shutdown drama | Powell heading before Congress News media has sought to 'delegitimize' Tulsi Gabbard, says liberal journalist MORE reveals why she decided against running for president in 2016 in a new book to be released Tuesday.

In "This Fight Is Our Fight," the progressive favorite recalls asking her husband, Bruce Mann, for his thoughts on a 2016 run for the White House. 

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 was floated by the more liberal wing of the Democratic Party as an alternative to Hillary ClintonHillary Diane Rodham ClintonDem strategist says Clinton ‘absolutely’ has a role to play in 2020 Left-leaning journalist: Sanders would be 'formidable candidate' against Trump Clinton hits EPA for approval of pesticide dump: ‘We need bees!’ MORE last year. In the end, Warren declined to run, opening the door for Vermont Sen. Bernie SandersBernard (Bernie) SandersSanders endorses Oakland teachers strike Dem strategist says Clinton ‘absolutely’ has a role to play in 2020 News media has sought to 'delegitimize' Tulsi Gabbard, says liberal journalist MORE to challenge Clinton for the Democratic nomination.

Many political observers now see Warren as a likely presidential candidate in 2020, when Democrats will be looking for a new standard-bearer to take on President Trump.

Despite Warren's refusal to run in 2016, she remained a target for Republicans during the election. During rallies, then-candidate Trump referred to her as "Pocahontas" as a way to make fun of her claiming Cherokee heritage. 

In her book, Warren talks about how the Clinton and Sanders campaigns both pressured her for an endorsement. 

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