I was first alerted to the Bernie Sanders rally by a Facebook invitation from a woman in the U.S. without documents who was organizing for the campaign.

The previous sentence is all one needs to know about why Sanders is burning up the 2016 Democratic presidential primary.

I was incredulous at first, because the invitation was for an event scheduled the next day. “Is this right?” I thought. “Bernie Sanders in San Diego? But the California primary isn’t until June.” But less than 24 hours later, 20,000 people were clamoring to see the socialist who is running for the Democratic nomination for president of the United States. (The next day, Wednesday, Sanders addressed an overflow crowd at Los Angeles’ Wiltern Theatre.)

The campaign rented the San Diego Convention Center, but it was too small to accommodate the crowd—the main arena was approved for only 10,000 people. The doors were to open at 5 p.m. I arrived at 4:15, and it took me 20 minutes to walk the circumference of the convention center and follow a winding, doubled-back-on-itself line of “Berners” that stretched to the San Diego harbor. As I approached the end of the line, I found myself walking alongside a black high school student. We marveled at the sight of so many people. I was beginning to despair at the length of the line, but instead of expressing frustration or disappointment, she uttered these remarkable words: “It gives me hope.”

Once inside, the scene was pandemonium. The crowd was youthful (not many outside of that age group have the stamina to endure such long lines) and diverse: white, Latino and Latina, Asian and a few blacks (we were in San Diego, after all). The enthusiasm, optimism and hope were palpable. The pre-speech chatter among the crowd was a preview of the stump speech most could recite by heart.

This crowd didn’t believe in Bernie Sanders as much as they believed Bernie Sanders. They believed that universal health care, free higher education, a $15-an-hour minimum wage and a return to democracy from plutocracy are all real and possible options, not just pipe dreams of an aged hippie. They believed that the richest nation on the planet can provide paid family leave for its citizens. They believed that they can make a difference.

Sanders’ speech, while predictable, was still exciting to hear, and it was stirring to witness the full power of the “Bern.” He employed an important rhetorical device that allowed him to avoid the egomania that infests other campaigns. At the head of each refrain he would begin with the phrase, “This campaign is listening to … women … young people … African-Americans … workers .… immigrants.”

The other candidates begin their pitches with “I”; Sanders begins with “This campaign.” While Donald Trump proclaims, “I will take care of women,” Sanders says, “This campaign” will stand with women as they fight for their right to earn equal pay for equal work. The best line of the night came after the candidate noted that Wal-Mart employees are forced to use billions of dollars in public assistance because the corporation pays its low-level workers so poorly. Sanders exclaimed that it’s time for the Waltons, the family that owns much of Wal-Mart, “to get off [corporate] welfare and start paying their workers a living wage.” And the crowd goes wild.

Who would have guessed that a 74-year-old would be the hipster candidate of 2016? Who would have guessed that a man would be the most compelling option for so many women in a presidential campaign featuring a female candidate? Who would have guessed that a Jewish socialist would be the candidate of choice for the black activist class?

The political split that Sanders has effected within the black community is explainable by several factors. The older black political class has strong party ties to Hillary Clinton and Bill Clinton going back over 20 years and six campaigns (two for Bill and four for Hillary). They have delivered their constituency early and often, to the great advantage of Hillary Clinton in this primary election.

But the young black activist class has connected to the Sanders campaign through social media, the Internet and its formidable ground game (of which these mega-rallies are the most visible dimension). The high school student I encountered in line had simply read about the candidates online and decided Sanders’ positions resonated more with her vision of her future than Clinton’s does.

While younger black voters have connected to the campaign around the issues of mass incarceration, universal health care, minimum wage and other current issues, the older black political class, by and large, is not familiar with Sanders. And the emails, social media and website sponsored by his campaign are not likely to find their way to my 90-year-old mother.

But a split of the black vote would be a win for the Sanders campaign, given his dominance among young voters, white voters, working-class voters and women (particularly young women). Sanders continues to grow his delegate count (he won two out of three states on “Western Tuesday”), and he keeps on drawing new supporters to his extraordinary candidacy.

My own evolution toward voting for Sanders has been a tortured one. I always agreed with him on the issues but worried about electability. My friends in the black political class will also privately support Sanders but firmly assert that once Republicans spend $500 million calling Sanders a “communist,” the current polls showing his advantage over Trump will evaporate.

But as I watch the Republican Party self-destruct, I see an opportunity for this election to represent a giant leap for American-kind. I actually relish a fall campaign that pits a fascist against a socialist. Finally, a real choice. I’m voting for Bernie Sanders.

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