SAN FRANCISCO — As Hillary Clinton heads into the first Democratic debate Tuesday, some of her top donors and allies are feeling encouraged for the first time in months.

But they’re also filled with deep anxiety about Joe Biden’s potential candidacy, a prospect that stands to sow the seeds of division just as they see Clinton moving beyond the email controversy to a place where her personality and policy command are breaking through.

Those conflicting feelings were on display at a private dinner in San Francisco on Wednesday night, where megadonor Susie Tompkins Buell held court before a group of about 15 major party donors and Clinton loyalists at Sam’s Restaurant, an old-school seafood joint where the waiters wear tuxedos, the sourdough bread is so legendary women cave in to carbs, and each table is curtained off for privacy.

Behind the thick brown curtain, the table was buzzing with excitement on the heels of Republican Rep. Kevin McCarthy’s comments suggesting that the Benghazi committee was created with the purpose of taking down the former secretary of state.

Yet the perceived gift from McCarthy did little to temper their angst about Biden’s intentions. The prospect of the grieving vice president’s potential entry into the race was a subject that obsessed the group over dinner, where many worried he will fracture the party.

The group – which included former Michigan Gov. Jennifer Granholm; major Obama bundler-turned-Clinton-supporter Wade Randlett; former ambassador to Hungary Eleni Kounalakis; Obama bundler Steve Spinner; Democratic fundraiser Mary Pat Bonner; and Steve Silberstein, a major Bay Area donor, and others – lifted their glasses to David Brock, the rightwing-hitman-turned-pro-Clinton crusader, and McCarthy, and drank.

"I'm concerned that the first bumpy road she hits – and there’s a man ready to knock her out, I’ve seen this before,” said Kounalakis, a close Clinton ally who is hosting a fundraiser in San Francisco for Clinton in November, and is viewed as potentially a major donor in 2016. “I’m worried we’re not accustomed to having a woman candidate at this level, and we don’t have the language to fight sexist attacks."

Buell, who over the past 10 years has given $25 million to progressive groups and candidates, shook her head at the prospect of a Biden candidacy.

“Why would he want to go out on such a negative?” she asked her friends. Buell has a complicated history with the Obama administration: she had a difficult time coming around to Obama in 2008 after he defeated Clinton in the primary, and refused to support his 2012 reelection, saying she was disappointed in how he was dealing with environmental issues.

Another supporter at the table said she was concerned that “if Clinton loses New Hampshire and Iowa, Biden will choose to get in,” while others expressed disgust at Biden’s appearance on the Colbert Report, which they said look staged, and like he was launching an opportunistic campaign out of grief. "It makes me out of my mind," one dinner guest complained.

Others simply dismissed the possibility that he will run. “At the end of the day, he doesn’t do it, he knows how disruptive it will be to our ability to win,” California Lt. Gov. Gavin Newsom told POLITICO before the dinner. He noted that he was so close with the Biden family that he named his son Hunter, the name of Biden’s younger son.

"Joe has run twice before, and he's lost twice before,” said another major fundraiser who backed Obama but is now committed to Clinton. “I don't think he's going to run, but it's incredibly cathartic."

The dinner, attended by a POLITICO reporter, was put together in honor of David Brock, who was in town for a talk about his new book, “Killing the Messenger: The Right-Wing Plot to Derail Hillary and Hijack Your Government.” He sat across from Buell and her husband, Mark, a brief moment of celebration during a grueling 28-city book tour that stretches through the primaries, and is organized some guidance from the Clinton campaign.

“Who wants tequila?” Buell, one of Clinton's closest friends, asked her guests, taking a survey of hands and ordering a round of tequila and sodas for the group. She then lifted her glass to propose a toast: “to David Brock and Kevin McCarthy!”

Twelve hours later, McCarthy would announce he was dropping out of the race for Speaker of the House.

The focus on Biden – and McCarthy’s remarks -- obscured the relative absence of discussion on the candidate currently leading Clinton in the polls in New Hampshire – Bernie Sanders. When the Vermont senator’s name surfaced, the group of stalwart Clintonites expressed confusion over how the 72-year-old pol has inspired enthusiasm among young voters, even young women. “Youth like anything different that feels rebellious,” Buell said. “They’re naive.”

Despite the tensions of the race, the group was in a positive mood. They were already celebrating McCarthy’s comment – a moment they saw as a turning point in what has been a brutal six months for those deeply invested, literally, in Clinton’s campaign and her future.

After months of frustration over the trajectory of Clinton’s campaign, Buell's dinner guests said they felt a positive shift in the primary dynamics in the ten days leading up to the first Democratic presidential debate.

They cited Clinton’s winning recent national television appearances – playing a bartender named Val on “Saturday Night Live,” and an interview with Savannah Guthrie on the Today show – and expressed relief that Clinton had finally made clear her positions on the Keystone Pipeline and the Trans-Pacific Partnership trade deal.

They even discussed plans for the general election, with Brock telling the group there would be a need for a “Republicans for Hillary” group to be formed after the Democratic National Convention.

“Starting July 1, it’s game on,” said a top Obama donor who’s well-connected in the White House and is supporting Clinton this time around. “Barack and Michelle are going to be the dogs of hell unleashed on the Republican party. They’re dying to do it for someone else. He will do what he does best and he knows where to be deployed.”

Mingling with guests before Brock’s book talk, Buell waved off nervous supporters who approached to ask how Clinton is holding up under the pressure.

“She’s fine, she’s fine. I just sent flowers to her home. I wrote, ‘we love you, Val,’” she laughed, a reference to the patient barkeep Clinton played last week on Saturday Night Live. “I think she’s getting advice from Val.”

As Brock’s book tour takes shape – he is currently on his seventh stop and plans to appear in Las Vegas during the debate – it’s becoming something of a sounding board for how Democrats feel about the state of the race. “If we had done this event at the end of August, it would have been entirely different,” Brock said over breakfast in Denver, after a book event hosted by megadonor Tim Gill and his husband Scott Miller.

Back then, Brock said, in the face of extended news conferences about the email even core supporters were unhappy with the state of play. “Now they seem like they’re in a much better place,” Brock said.

Yet in a sign of the unsettling effect Biden could have on the Democratic primary, Gill and Miller told POLITICO they had donated $50,000 to the Draft Biden campaign, and that Miller had stepped down from the board of Correct the Record, one of Brock's pro-Clinton groups, in anticipation of a potential run by Biden. But they said they planned to continue giving money to Clinton, as well.

At a book event held at the Century Club of California, Buell, who is a major donor to Brock’s web of organizations, bragged about how much Bill Clinton enjoyed Brock’s latest book, despite a harsh review from the New York Times dismissing it as “an extended press release.”

After receiving a copy from Brock in the Hamptons last August, “Bill stayed up all night and read it, and called him in the morning and thanked him and said it’s the best thing that’s been written about this,” Buell boasted to the audience. “I don’t know what we would have done if David hadn’t done what he has done.”

“You’ve been at the water cooler,” Brock said. “This book is for Hillary supporters to be able to talk about these issues, whether it’s Benghazi, or that she was a do-nothing Secretary of State, or email, email, email, or she’s too inauthentic, or she’s a bad candidate – I refute it. We can’t allow this garbage to stand in the way.” The crowd cheered.

In another speech he delivered in San Francisco on Monday, Brock even moved beyond defense and played offense, defending Clinton's progressive bona fides.

"Hillary Clinton isn't Saul Alinsky, though she did write her college honors paper about him," he said, in a copy of his remarks reviewed by POLITICO. "Hillary Clinton isn't Elizabeth Warren, though she's supported many of Warren's reforms.... Hillary is the real progressive champion in this race."

But some who attended his event last week still harbored concerns.

“What I worry about is women who are my age, 67, pro-Hillary all the way the first time, and who now say, I just don’t believe her,” said JoAnn Loulan, development director at the Progressive Women Silicon Valley. “I worry about Hillary supporters that aren’t going to vote for her,” she said.

“It’s affecting people,” Brock conceded. “I see it. I travel around the country, I’m aware of it. This is what a smear campaign is. It’s exactly what it is.”

He admitted that the enthusiasm for the campaign may be late to develop.

“When we get to that general election, given the stakes, people are going to get the stakes – protecting the Supreme Court, protecting and expanding on President Obama’s legacy,” he said. “It’s going to get exciting, and people are going to get excited.”

Brock compared the situation now to the 1990s, when the Clintons were mired in scandals from Whitewater to Monica Lewinsky to impeachment.

“There were panicky Democrats, sure,” he said. “Nothing came of a thing. How did it end? It ended with Bill Clinton with sky high approval ratings and Hillary in the Senate. That’s how I think this is going to end.”