LIVE FROM MANCHESTER, on Saturday night, supporters of Elizabeth Warren cheered loudly for Joe Biden as he spoke at the New Hampshire Democratic Party’s marquee fundraising event. Deval Patrick’s section roared for Pete Buttigieg.

And the Bernie Sanders supporters directed derisive chants towards Pete Buttigieg. They then interrupted Amy Klobuchar, who gave a casual look to their corner of the stadium and said, “Hi, Bernie people!

Sanders, who was up by more than 7 points in the polling average, gave his standard stump speech, with notes of harmony but no sign of reeling in his jeering section.

A few hours later, Larry David opened “Saturday Night Live” with an homage to that crowd’s infamous online persona: “I don’t know how or why it happened, but I am king of an army of internet trolls called Bernie Bros. Could I stop them in their tracks? Of course. Should I? Yes. Will I? Eh.”

The indifference of Bernie Sanders to the aggression of his (very) online fans was a distraction during the competitive parts of the 2016 primary. That sideshow had more practical implications once Sanders refused to step aside after Hillary Clinton’s nomination became inevitable. The defection of Sanders’s primary election supporters to Donald Trump is overstated — Democrats actually lost fewer Sanders supporters in 2016 than Clinton supporters from her 2008 primary loss.

But the narrative importance of the Sanders movement not dividing the Democratic Party will be evident through November regardless of how the primaries unfold.

If Sanders victories mount and the Revolution does come to pass, will his supporters enjoy the moment or turn off mainstream voters by lashing out?

If Sanders continues to win just 25 percent of voters (while a nice figure in a crowded primary, 25 percent is not a Revolution) and loses by delegates or at the convention, will such animus be directed at Trump or towards the Democratic nominee?

As election results came in on Tuesday evening, it became apparent that Sanders’s lead had nearly vanished. Buttigieg overperformed his polls by 3 points while Sanders had fallen by the same amount, leaving a margin of just 1.5 percentage points. Third-place finisher Klobuchar had jumped 8 points in the final days.

Those late changes led to a trio of victory speeches: Klobuchar for winning momentum, Buttigieg for again basically tying after Iowa, and Sanders for winning a plurality.

In each, as in Elizabeth Warren’s early speech, unity was the theme and Trump was the common enemy.

Yet like on Saturday night, Sanders supporters were the lone aggressors at election parties, again booing and chanting derisively at Buttigieg during his speech.

It took less than a day for such behavior to blow back on the candidate. The single most important union to any early primary state, the “political kingmaker” Culinary Workers Union representing 60,000 workers in Nevada, released a statement on Wednesday that “It’s disappointing Senator Sanders’ supporters have viciously attacked the Culinary Union & working families in NV simply because we provided facts” about Medicare for All.

No candidate wants to elevate a clearly negative story. And a powerful labor union disagreeing with the most pro-labor candidate on the highest-profile position any candidate has on voters’ top issue certainly qualifies as a negative story. Like an unruly high school basketball crowd that earns its team a technical foul after a warning, it seems that for some Sanders supporters the negativity is actually the point. When that occurs, the coach takes the microphone and the crowd complies.

As Larry David dryly noted, “of course” Sanders can and should bring his supporters in line. While their defection to Trump may have been overstated in 2016, they will play a major role in how voters across the anti-Trump spectrum view the parties heading into November, regardless of the primary outcome.

Democrats can be a party of unity despite disagreement. Or they can be seen as a jeering arena crowd and accompanying online mob attacking labor unions who dare to spread facts about relevant policy.

It is time for Sanders to curb his online army’s enthusiasm for going on the attack. Grab the mic, Bernie.

Liam Kerr is co-founder of The Welcome Party, a Boston-based effort to engage independent and moderate voters on behalf of a “big-tent” Democratic Party.