Nevada supporters of presidential candidate Bernie Sanders engaged in a shameful display of mob anarchy at that state’s convention on Saturday, and so far the Vermont senator’s response has fallen far short of the leadership needed in such a volatile situation.

Political conventions can be passionate gatherings, and activists have been known to parade, protest, clap, shout and engage in all manner of boisterous activity. But throwing chairs, hurling obscenities at party leaders and shouting down keynote speaker Sen. Barbara Boxer to the point where she feared for her safety? And making death threats against the party chair because you don’t like the way things turned out? No.

Sanders supporters became enraged when they realized that Sanders would not get more delegates to the national convention than Hillary Clinton, who, after all, won that state’s caucuses back in February. It is understood that some Sanders followers are new to the political party process — dozens were disqualified from delegate duty because they failed to register as Democrats by the convention deadline. That does not excuse their taking a political process designed to ensure the peaceful passage of power and transforming it into a gutter brawl. State party Chairman Roberta Lange was subjected to threats against herself and her family in more than 1,000 calls and texts, many so vile they could not be printed here. Said one texter: “Prepare for hell. The calls won’t stop.”

Sanders must take some responsibility for things spinning out of control. He has repeatedly called for a “political revolution,” and blamed “closed primaries” — primaries limited to, of all things, Democrats — for poor showings. He has long fomented the notion that the party he has scorned but now wants to lead is “ideologically bankrupt.” This has given rise to contempt among some of his supporters for the party nominating process and now appears to be culminating in an intolerable level of aggression.

U.S. Senate Minority Leader Harry Reid, D-Nev., appealed directly to his colleague earlier this week and said he was confident Sanders would do the right thing, noting that his response would be a test of leadership.

If so, Sanders failed. What he offered Tuesday was a token condemnation of the chaos that erupted, reserving most of his written statement for a rebuke of Nevada’s Democratic leaders for using their “power to prevent a fair and transparent process from taking place.”

The ill will has only grown since Saturday, with some supporters publicly saying there could be trouble when Democrats convene in Philadelphia to choose a nominee in July. Sanders must take action now to broker a peace among the party he has split. That will call for more than a token statement.