CLEVELAND — Anti-Trump forces organized an unprecedented protest against Donald Trump’s nomination as GOP presidential candidate, throwing the convention floor into chaos on Monday afternoon.

Anti-Trump forces were trying to challenge the rules so that delegates could vote their personal preference, which might have endangered Trump’s nomination—or at least wounded the presumptive nominee.

What followed was a sensational show of opposition to Trump’s coronation on the opening day of the Republican National Convention.

After being resoundedly defeated in the convention’s rules committee last week, anti-Trump delegates gathered signatures from the majority of delegates in nine states, requesting a state-by-state roll-call vote of the rules package on the convention floor.

The group responsible for the petition, Delegates Unbound, submitted the petition to the secretary of the convention early Monday afternoon. The petition called for every convention delegate to vote individually—in a roll call vote—on the rules committee report. The rules report paves the way for Trump’s nomination by binding delegates to vote for the candidate according to each state’s primary results—and Trump clinched the nomination according to those primary election results.

When the rules committee chairperson gaveled the delegates into session, the chair presiding over the convention, Rep. Steve Womack, called a voice vote on the rules package and determined that it had been approved.

As anti-Trump delegates demanded a roll-call vote, Womack left the stage.

The arena erupted.

After shouting and chaos on the convention floor, Womack returned, announcing that the motion for a roll-call vote had support from only six states, which is one less than the number needed to force a roll call vote. In the intervening time, three state delegations had been convinced to withdraw their request to be counted.

So instead of a roll call, which would have recorded each delegates vote individually, the chairperson held a voice vote. The convention hall erupted in shouts from delegates, much of which was indistinguishable—and then the chairperson declared again that yeas had won.

The scene inside the convention center in Cleveland differed markedly from the way the chaos was presented on television. Without access to live microphones, anti-Trump delegations were not heard as the shouted for the chair’s attention. But on television, the microphones were running—giving the viewer a dramatic account of the resistance from delegations resistant to Trump.

“Rigged election,” read a mass text from the anti-Trump group Delegates Unbound. “Walk out.”

“What happened is, the Trump-RNC forces went around to people and asked them to say they didn’t mean to sign,” Eric O’Keefe, a Delegates Unbound organizer, told The Daily Beast as he watched anti-Trump delegates continue to protest on the floor below the stadium seats. “So we’re seeing the staff steal the party from the delegates.”

“This is an absolute affront to all these delegates,” said Delegates Unbound leader Dane Waters. “So you have one guy standing there gaveling down when clearly the delegates wanted to do something else.

Gary Teal, an organizer with Delegates Unbound and vice-chair of the DC party, said that he did not think the anti-Trump forces could have actually blocked Trump’s nomination. Teal did say, however, that he thinks the procedural maneuverings may inflame anti-Trump forces further.

“I think it’s shocking, because I don’t think it was politically the right thing to do,” Teal told The Daily Beast. “I believe it would have been smarter for them to let people have a roll call vote.”