Sen. Elizabeth Warren Elizabeth WarrenWarren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon No new taxes for the ultra rich — fix bad tax policy instead MORE (D-Mass.) is urging Democrats to focus on combatting the Trump agenda, lamenting that he's been in the White House for less than 100 days.

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Warren — who joined the Senate in 2013 and quickly became a liberal favorite — details in her new book why she decided against running in 2016.

She's up for reelection to her Senate seat next year and is expected to run for a second term.

Questioned on if she regrets not running last year, Warren said what she regrets is that Trump is president "full stop, right there. ... [But] he is and we've just got to go forward."