PHILADELPHIA–The Liberty Bell, on permanent display here at Philadelphia’s Independence Mall, is known for its famous fracture. The bell was cast in London in 1751, and cracked on its first test ring. The bell was molten down and recast in Philadelphia, and rang from the Pennsylvania State House, now known as Independence Hall, for close to 100 years. A second crack formed years later, and the bell eventually was decommissioned, taking on the symbolic significance it has today, inspiring movements to abolish slavery, for women’s suffrage and others. The Democratic National Convention here this week also is inspiring many, in movements for LGBTQ rights, gun control, and racial and economic justice and beyond. But as the first woman in U.S. history is nominated to be the presidential candidate of a major party, a deep split in the Democratic Party has emerged. Sen. Bernie Sanders conceded to Hillary Clinton and endorsed her candidacy, but many of his supporters have not. Hundreds of them walked out of the convention as Clinton’s nomination was formalized Tuesday night.

The nomination of Hillary Clinton is historic. She has a significant chance to be the first woman president of the United States. During the roll call at the DNC, the delegation from Vermont, Sanders’ home state, passed, and was thus called on as the last state to report, after Wyoming. The Vermont spokesperson stated the delegate votes, then Bernie Sanders, whose insurgent campaign rocked the Clinton juggernaut to its core, stood and took the microphone:

“Madam Chair, I move that the convention suspend the procedural rules. I move that all votes, all votes cast by delegates be reflected in the official record, and I move that Hillary Clinton be selected as the nominee of the Democratic Party of the United States.” The actual delegate counts of Clinton versus Sanders were dispensed with, and Clinton was nominated “by acclamation.”

Cheers and applause filled the Wells Fargo Center. While thousands went wild, several hundred, well, just went. Chanting “Walk out, walk out” and “This is what democracy looks like,” 300 Sanders delegates, including many from Vermont who were standing with Sanders moments before, marched out of the arena and proceeded to the media tent to demonstrate their disagreement with the process and announce the “No Voice, No Unity” campaign.

“We were never welcome here, we were never wanted here,” Sanders delegate Felicia Teter told the “Democracy Now!” news hour as she walked out. “The people’s voices are not being heard, and still the people’s votes are not being counted. We are going to show the Democratic Party that if they will not have us and they will not welcome us into their party, then we will leave, and they will lose to Trump. And it will not be our fault. It will be their fault, because they did not listen to the people. … They simply ignored us. They shut us down.”

Many Sanders delegates cited issues on which they strongly differ with Hillary Clinton, from her earlier support for the Trans-Pacific Partnership (TPP) and not knowing where she stands on it today, to her coziness with Wall Street, to her consistent support for ever-widening wars in the Middle East.

The walkout also was fueled by leaked Democratic National Committee emails that were posted online by WikiLeaks just days before the convention. Some of the emails proved that the DNC, and its chairperson, Congressmember Debbie Wasserman Schultz, actively worked to disparage Sanders and his campaign. The emails led the headlines all weekend; by Monday, Wasserman Schultz had announced her resignation as DNC chairperson. Bernie Sanders had for months accused the Democratic National Committee of bias in favor of Clinton throughout the campaign. Now his supporters had proof, and many carried signs that read “Rigged” as they walked out.

The Liberty Bell was decommissioned because of a barely visible hairline fracture. The famous crack in the bell was actually made on purpose, in an attempt to repair it. The Democratic Party has an enormous challenge now, to unify its members to defeat one of the most bigoted and divisive, some say fascistic, presidential candidates in modern U.S. history, Donald Trump. The party has a very deep and visible fracture. The question remains whether they can repair the crack in time to defeat Trump.