Story highlights Elizabeth Warren and Bernie Sanders appeared at a campaign event for Hillary Clinton in Denver

At the event, the liberal favorites mocked Trump, making the case for Clinton to college students

(CNN) Sens. Elizabeth Warren and Bernie Sanders appeared together Sunday at a campaign event for Hillary Clinton in Denver, and tore into Donald Trump as they pressed Clinton's case to college students.

Warren called the Republican Party's presidential nominee a "selfish little sleaze ball" who "will never be president of the United States." She sought to convince millennial voters -- who have remained somewhat resistant to Clinton after her contentious primary fight with Sanders -- that his efforts to move the party left had been rewarded.

"I am proud of the debate that Bernie Sanders and Hillary Clinton had in our primary, way to go. I am proud that we are party that doesn't debate who has the smallest hands, or who can build the longest, tallest, fake gold-plated wall in the world. I'm proud that we are not looking for the most obscene way to demean women," Warren said.

The progressive firebrand also pointed to the 2016 Democratic platform, which included a series of policy compromises hammered out by the Sanders and Clinton camps ahead of the party's convention, as an example of what a unified party could achieve.

"Thanks to Bernie Sanders, we have the most progressive Democratic platform in American history," Warren said.

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