Sanders told CNN's Erin Burnett on "OutFront" that more than 100 protests would take place around the country on Saturday demanding politicians meet with their constituents to hash out concerns over the Republican agenda after weeks of raucous town hall events.
"I think the Republicans have not seen anything yet," Sanders said. "If they're worried about the protests they're seeing, they're going to see more. This coming Saturday we believe there will be well over 100 protests, most of them in Republican offices around the country, district offices, demanding that Republican members of Congress meet with their constituents and answer the questions that their constituents have."
He dismissed Republicans, like Texas Rep. Louie Gohmert, who have said they are forgoing town hall events over safety concerns.
"If you don't have the guts to face your constituents, then you shouldn't be in the United States Congress," Sanders said. "That's what you're elected to do."
He also slammed the tea party movement as he defended the many people who have shown up to town halls and been accused by the President and others of being paid protesters.
"Unlike the tea party this is not being funded by the billionaire class," Sanders said.
Challenged on that point and reminded that after the rise of the tea party, Democrats posted major losses in the 2010 midterm elections, Sanders talked about the current groundswell of people at town halls and did not back up his comments.
Burnett asked Sanders about "We Will Replace You," a group that includes some who said they supported Sanders' presidential campaign and has vowed to run primary challenges against Democrats who it views as not sufficiently opposing Trump's agenda.
Sanders said, "It's a free country, and people can do whatever they want to do." Adding that he didn't know exactly what the group's demands were, he called on Congress to join a populist movement in opposition to Trump.
"We need a mass movement of people, and I think we need members of Congress actively involved in that movement," Sanders said.
Pressed on the group, Sanders said again he was unfamiliar with what it stood for and that its members could do as they pleased.
"You're asking me about a small group of people who do a very good job in getting publicity. I don't know what that means," Sanders said. "What you have to do is look at the totality of what a candidate does. If you don't like the candidate, fine, don't support that candidate. Do what you want."