CLIVE, Iowa — Campaign surrogate Rep. Rashida Tlaib on Friday night booed Hillary Clinton from the stage of a Sen. Bernie Sanders event.

With Sanders stuck in Washington due to the Senate impeachment trial, the campaign has had to lean more heavily on surrogates to energize voters in the days leading up to the caucus.

As part of the Friday night concert featuring indie folk band Bon Iver, Tlaib participated in a panel discussion along with House colleagues Reps. Ilhan Omar and Pramila Jayapal.

As they were about to wrap up, moderator Dionna Langford, an Iowa-based activist, brought up recent comments by Hillary Clinton that nobody liked Sanders. At the mention of Clinton's name, scattered boos could be heard among the fired-up crowd.

"We're not gonna boo; we're not gonna boo," Langford said, attempting to calm the audience. "We're classy here."

Tlaib interjected, "I'll boo." Then she booed from stage, leading the crowd in another chorus of boos.

"You all know I can't be quiet. No, we're gonna boo," she repeated. "That's all right. The haters will shut up on Monday when we win."

The bitterness from the 2016 Democratic primary has not fully abated among Sanders supporters. Many of his supporters still believe that he was denied the nomination by a rigged system that favored the more establishment-friendly Clinton.

Earlier in the night, the crowd booed the Democratic National Committee when filmmaker Michael Moore ripped the party for changing debate rules so that billionaire Michael Bloomberg would be able to participate in debates despite not having any individual donors.