"I don't have to tell anybody here that our country today faces enormous problems," he said outside of a Senate Democratic retreat in West Virginia. "We have a delusional president, who is way out of touch with the needs of the people of West Virginia and working people all over this country."

.@BernieSanders grabs the bullhorn to address assembled crowd outside the private Senate Democratic retreat in West Virginia pic.twitter.com/NCxVlgy45f — Phil Mattingly (@Phil_Mattingly) January 26, 2017

Sanders added that the only way Democrats could "beat" Republicans is "through a massive grassroots effort."

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"We saw what that grassroots effort is about on Saturday with the women's march all over America," he said, referring to worldwide marches that drew millions of people, to yells and cheers from the protestors.

Warren added on Thursday that protestors had to be ready to "fight back" against the unified GOP government.

"The Republicans have the power in Washington. They have the Senate. They have the House," she said to boos from the crowd. "They have the White House, so it is now up to us."

She added that "we can whimper, we can whine or we can fight back. ... Are you ready to fight back?"

Senate Democrats are holding a closed-door retreat this week in West Virginia, which Trump carried by more than 40 points, while congressional Republicans huddle in Philadelphia.