The next few weeks will show whether Bernie Sanders can expand his support beyond those who want a political revolution — much as he did in winning California on Super Tuesday.

The upcoming weeks will also show if Joe Biden can maintain the momentum that brought him victories in 10 of 14 primary election states Tuesday and vaulted him into the delegate lead for the Democratic presidential nomination, or whether he will undermine his candidacy with more rickety debate performances and stumbles on the trail.

But Sanders faces a greater urgency to broaden his appeal, because much of his Super Tuesday support was attributable to votes cast before Biden revived his campaign by winning Saturday’s South Carolina primary, said Dave Wasserman, an editor with the nonpartisan Cook Political Report, which analyzes federal races.

“And he still fell well short of Biden,” Wasserman tweeted. “That’s why this race could functionally be over soon.”

Keep in mind: a ton of the votes/delegates Sanders won yesterday are attributable to votes cast *before* SC and before Buttigieg/Klobuchar dropped out.



And he still fell well short of Biden. That’s why this race could functionally be over soon. — Dave Wasserman (@Redistrict) March 4, 2020

Sanders’ actions Wednesday were seemingly contradictory. The Vermont senator both extended an olive branch to fans of Barack Obama and alienated other Democrats.

He released a new ad showing the popular former president, perhaps the ultimate establishment Democrat, praising Sanders in 2016 as someone who has “great authenticity, great passion, and is fearless.”

Hours later at a news conference, Sanders railed on “the entire political establishment ... an establishment that is working frantically against us.”

“What this campaign is increasingly about,” Sanders said, “is, ‘Which side are you on?’ ”

Some of the challenges facing Sanders:

Getting young people to vote: Sanders told The Chronicle on Sunday that “Democrats win elections when voter turnout is high. ... Does anyone really think that a Biden candidacy will create the kind of energy and excitement we need to significantly increase the voter turnout?”

But young people, a key component of Sanders’ envisioned coalition, aren’t turning out.

Roughly 1 in 8 voters Tuesday was under 29, according to exit polls. Meanwhile, almost two-thirds were older than 45 and about 30% were older than 65 — people also known as “Biden voters.”

Sanders acknowledged that Wednesday, noting that “historically,” the young don’t vote in numbers as great as those of the old.

“We have not done as well in bringing young people into the process,” Sanders said. “It is not easy.”

Making some Democratic friends: Biden’s campaign turned around when Rep. Jim Clyburn, D-S.C., endorsed him in South Carolina days before the primary. Most endorsements don’t matter, but that one did — Clyburn has unsurpassed credibility with fellow African Americans in his state.

He’s also the No. 3 House Democrat, making him a member of the “establishment” that Sanders relentlessly criticizes. So is Amy Klobuchar, the Minnesota senator whose last-minute withdrawal from the race and endorsement of Biden delivered her state to the former vice president.

Sanders isn’t even a Democrat — he caucuses with the party in the Senate, but he’s an independent. He can continue to alienate establishment Democrats with us-against-them rhetoric, if he doesn’t mind losing more states.

Changes are coming soon, Fremont Democratic Rep. Ro Khanna, a national co-chair of Sanders’ campaign, told The Chronicle. Khanna expects Sanders to start talking more positively about the Democratic Party.

“We need to convey how proud we are of the Democratic Party, from FDR to Obama, and how we want to complete the project of the New Deal,” Khanna said. “You’re going to hear much more about expanding the coalition, reaching out to leaders in the Congress, the nonprofits and in the grassroots.”

Finding revolutionaries in the suburbs: Sanders acknowledged Wednesday the difficulty of assembling his coalition without the support of super PACs or private fundraisers.

“What we are trying to do is unprecedented. We are talking about a political revolution. We are talking about bringing millions and millions of people who have no voice, who have given up on the political process,” into the process, Sanders said. “It’s not easy.”

Yet Democratic voters are with Sanders on his signature issue — a Medicare for All, government-run health plan. Exit polls Tuesday showed that that most voters backed replacing private health insurance with a single-payer government plan. Many of those voters backed Sanders, but not in the overwhelming numbers one would expect given his full-throated support of the idea.

Khanna sees potential for Sanders to connect with suburban voters. Look no further than the Bay Area, where Khanna points out that Sanders won the Silicon Valley counties of Santa Clara and San Mateo.

“Sanders carried some of the most affluent suburban counties in this country,” Khanna said. “That is because his message is resonating — it is one of economic opportunity,” particularly his support of tuition-free college.

Getting supporters to tone it down: Several times during his remarks Wednesday, Sanders said that “I like Joe,” perhaps in an effort to blunt the nasty tone of a small percentage of his supporters.

Former candidate Pete Buttigieg criticized Sanders for the actions of his supporters last month, saying, “We can build a movement without having legions of our supporters online and in person attacking Democratic figures and union leaders alike.”

Sanders said he didn’t want the campaign to “degenerate into a Trump-type effort where we are attacking each other with personal attacks. That is the last thing this country wants.”

It’s worth watching how the Sanders camp handles Massachusetts Sen. Elizabeth Warren, who had a terrible Super Tuesday and is reportedly weighing her options. For several days, Sanders supporters have urged Warren to drop out and endorse Sanders, using the hashtag #WarrenEndorseBernie.

Some Warren supporters didn’t appreciate the advice. “I can’t think of anything more insulting than telling Warren to endorse Bernie,” one tweeted.

Sanders tried to tamp down the talk Wednesday, saying it was important for “all of us — certainly me, who has known Elizabeth Warren for many, many years — to respect the time and the space that she needs to make her decision.”

Warren is one establishment figure who might be able to help Sanders navigate these next few weeks. If she does bow out, a Morning Consult poll says Sanders is the second choice of 40% of Warren supporters, while Biden is the second pick of 16%.

Joe Garofoli is The San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli