(CNN)Massachusetts Sen. Elizabeth Warren said it was time for voters of all stripes to unite together against GOP front-runner Donald Trump.
Elizabeth Warren: 'Trump is a bigger, uglier threat every day'
"Donald Trump is a bigger, uglier threat every day that goes by -- and it's time for decent people everywhere -- Republican, Democrat, Independent -- to say, 'No More Donald,'" Warren wrote Monday in a Facebook post.
Warren, who's not endorsed a Democratic candidate, is an outspoken liberal voice in Congress.
"There's a history of demagogues calling those they disagree with 'terrorists' and using that as justification for intimidation and violence -- and that history is ugly and dangerous. There's also a history of people staying quiet for too long, hoping for the best but watching silently as the threat metastasizes," Warren wrote.
The comment comes after the GOP presidential front-runner's rallies have turned increasingly violent in the past week as supporters clashed with protesters. Trump was forced to cancel a rally in Chicago over the weekend and was given a scare when a protester rushed the stage Saturday.
Meanwhile Trump has said he is considering paying the legal fees for a supporter charged with assaulting a protester at a North Carolina rally. And a former Breitbart reporter filed an assault charge against Trump's campaign manager Corey Lewandowski, alleging he yanked her violently from Trump last Tuesday.
"It's not violent. It's a protester that stand up or probably a disruptor, because I think they're sent there by people on the other side," Trump told CNN's Wolf Blitzer on Monday.
Trump added: "But there's no violence, nobody's been hurt."
House Speaker Paul Ryan said in a radio interview on Monday that the violence at Trump's events were very concerning and "there is never an excuse for condoning violence, or even a culture that presupposes it."
"There's no virtue in silence," Warren wrote.