If presidential hopeful Bernie Sanders has learned anything over the past month after being interrupted at two major rallies by demonstrators with the Black Lives Matter movement, it's that when directing preemptive action, the third time's the charm.

Two days after the 73-year-old junior Vermont senator was heckled by Black Lives Matter activists at a Seattle event, Sanders vowed at a Los Angeles arena Monday night to fight harder to "end institutional racism" than any other candidate vying for the presidency in 2016. He even opened his evening lineup with words from his new national press secretary, who is black, and a staunch supporter of the Black Lives Matter movement.

"It is very important that we say the words 'black lives matter,'" Press Secretary Symone Sanders — no relation to Bernie — said in her opener to a crowd of roughly 27,000, including 16,000 inside the arena and thousands more gathered outside, according to the campaign.

"But it's also important to have people in political office who are going to turn those words into action," she added. "No candidate for president is going to fight harder for criminal justice reform and racial justice issues than Senator Bernie Sanders."

The crowd roared and cheered as Sanders spoke, but there were no interruptions at the event Monday, although the crowd was peppered with an unknown number of grassroots activists, some holding signs that read "Black lives matter," and "Black vote matters."

Activists have also initially responded positively to Sanders's new Racial Justice platform, which addresses political, legal, and economic violence waged on minorities.

The 'violence' framing in the initial draft of the Sanders Racial Justice platform is powerful. & I look forward to seeing him expand this. — deray mckesson (@deray)August 10, 2015

So far, Sanders has been riding a wave of popularity that has been centered on his progressive economic policies. He's spoken to record-breaking crowds, where tens of thousands of supporters have turned up. At these events, supporters have challenged other 2016 presidential hopefuls to "Feel the Bern" — a popular mantra that's taken aim at the wide GOP field and fellow Democrat Hillary Clinton alike. Sanders' blockbuster rallies have so far outstripped even election frontrunners, with Clinton's largest so far topping roughly 5,500.

But while the self-styled "democratic socialist" has focused his efforts on economic inequality, Black Lives Matter activists have been challenging Sanders to also explicitly address systemic racial inequality — not as a result of bad economic policy, but to acknowledge it as its own emergency. The push comes in the face of the mounting deaths across the country of unarmed black people in police custody, and as America's disproportionate sentencing and mass incarceration has come to the fore, as have a raft of other race-based issues.

At the annual liberal Netroots Nation conference in Phoenix in July, Sanders was accused of dismissing these issues and the protesters who began chanting "say her name," in reference to Sandra Bland, an unarmed black woman who died recently in Texas police custody, and "black lives matter," during his speech. Responding at that event, Sanders noted he would not "out-scream people," and brought up his 50-year record on "fighting for civil rights and dignity."

These disruptions have created a rift among the liberal base. Many supporters have pointed to Sanders's historic background supporting civil rights, from as early as the 1960s when he marched with Dr. Rev. Martin Luther King and joined nonviolent protests — and even criticized the "interrupters" as impolite, obstructing to the cause, or unwelcoming to supporters and allies.

On the other hand, these actions are being defended as a push for structural change in American society, especially when it comes to racial bias — which historically has not come about by asking politely, but through the disruptions and protests of activists and leaders such as King. As a self-proclaimed progressive liberal, Sanders is positioned to meet calls from activists to directly address institutionalized racism, they contend, especially where Republican candidates have chosen to remain silent or reject these as non-issues.

Ultimately, Sanders has agreed with these contentions, and on Monday, took a decidedly candid stance on race, telling a raucous crowd in LA, "There is no president that will fight harder to end institutional racism."

At an earlier and smaller event in Oakland on Monday, Sanders also took up the subject before members of National Nurses United, the country's biggest nursing organization, with 185,000 members, which formally endorsed him that day.

"When we talk about creating a new America, at the top of our list is the end of racism in all its ugly forms," Sanders said at the Oakland event. "All of us were nauseated, when we have seen the videos... we know that if those folks were white they would not be dragged out of cars and thrown into jails."

When an attendee yelled, "Senator, do black lives matter to you?" he replied, "Yes."