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CLEVELAND, Ohio — Massachusetts Sen. Elizabeth Warren spent a weekend in Ohio revving up Democratic base voters by laying into Republican Donald Trump, calling him everything from a “nasty little bully” to a man with a “dark and ugly soul.”

In Cleveland on Sunday, Warren targeted him for “inviting his followers to commit a terrible act of violence on his opponent,” charging only “a little bully who can’t win in a fair fight” would do such a thing.

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Warren added that “Trump has led the charge on the "birther" movement and only when his handlers tied him down and made him did he finally admit that it wasn’t true.”

“What kind of a man does that? A man with a dark and ugly soul. A man that will never be president,” she said.

Warren: Trump "led the charge on the birther movement...what kind of a man does that? A man with a dark and ugly soul." — Alexandra Jaffe (@ajjaffe) September 18, 2016

Warren says Trump has "repeatedly invited his followers to kill another human being...what kind of a man does that?...a nasty little bully" — Alexandra Jaffe (@ajjaffe) September 18, 2016

Ohio remains a key swing state, particularly for Trump, whose path to the White House narrows considerably without the state. But recent polls have shown the Republican opening a slight lead on Clinton, and Democrats are concerned he could win the state if their voters stay home.

To avoid that possibility, the Clinton campaign dispatched two of the liberal movement’s most beloved figures this weekend to rev up millennial voters weekend: Warren and Vermont Sen. Bernie Sanders, both of whom delivered red meat to the liberal base at college campuses across Ohio.

Both Sanders and Clinton attacked Trump on his history of supporting the "birther" movement and what they described as the “bigotry” of the GOP candidate.

“Donald Trump calls African-Americans thugs and Muslims terrorists and Latinos criminals — and Rob Portman and the Republican Party still back him,” Warren said Sunday. “We believe that racism and injustice and bigotry have no place in this country. That black lives matter!”

Related: Elizabeth Warren Calls Trump 'Small, Insecure Money-Grubber'

But both of their remarks were focused more on the GOP nominee and the Democratic agenda than Clinton specifically, hinting at the hill she still has to climb in winning over Democratic skeptics and energizing the Democratic base. Many young voters in particular remain disillusioned with the nominee, after supporting Sanders during the primary and coming up short.

And in Cleveland on Sunday, that persistent dissatisfaction within the party was vividly on display — a small group of young attendees shouted out in protest that “Bernie was robbed!” during Warren’s remarks, chanting “Jill not Hill” as they walked out — a reference to Green Party nominee Jill Stein. Democrats have expressed concerns protest votes for Stein could cost them a win in tight states this fall.