SAN FRANCISCO — As the photo shoot in front of the Mike Bloomberg campaign bus wrapped up Monday, former Philadelphia Mayor Michael Nutter got some news. A volunteer held up her phone and called to the crowd outside the local field office.

“Amy’s getting out," she said.

Nutter confirmed that Sen. Amy Klobuchar had quit the Democratic presidential race on his own phone as he climbed into an SUV for the next of five California stops to campaign for Bloomberg.

“And then there were four,” Nutter said. (Klobuchar endorsed former Vice President Joe Biden that night.)

Bloomberg, the billionaire former mayor of New York, made his debut on the ballot Tuesday, when the 14 Super Tuesday states held primaries. The first contests for Bloomberg followed a decisive Biden win in South Carolina, and a slew of endorsements, including from former centrist rivals Klobuchar and Pete Buttigieg. And polls showed Sen. Bernie Sanders, now the clear Democratic front-runner, poised to win a large share of California’s 415 delegates.

Late Tuesday, Bloomberg was well behind in the states that had reported results, a poor showing that could undercut his electability argument.

Bloomberg has said the party will lose if Sanders is the nominee. Nutter, Bloomberg’s national political chair, said Monday he also “has a lot of concerns” about a self-described democratic socialist at the top of the ticket. But now that it’s just Bloomberg and Biden in the moderate lane, does Nutter fear his efforts could help Sanders?

“We haven’t even given folks the opportunity to even vote for us yet,” Nutter said. “It’s like saying a team shouldn’t show up before the season even starts. Voters will have a full opportunity to make some serious decisions come Tuesday.”

In recent weeks, Bloomberg jammed the airwaves with ads in all the Super Tuesday states, traveling to them and dispatching surrogates, who include a small army of city mayors who back him. The big question for him Tuesday was whether his $500 million political experiment would create a path to the nomination.

On Monday, Nutter made stops in Oakland, San Francisco, and Sacramento before flying to Palm Springs and, on Tuesday, San Diego. While Nutter has kept a low public profile in Philadelphia since leaving office four years ago, he traveled to 12 of 14 Super Tuesday states, adept, from years in the hot seat, at defending Bloomberg on controversial issues like stop-and-frisk policing. He’s also a skilled mingler who seems to be genuinely enjoying himself.

“Obviously tomorrow is an incredible day for us," Nutter told a crowd of San Francisco volunteers Monday, holding signs that said “Ganamos con Mike” (‘'We Win with Mike") and “California for Mike." "We’re on the ballot tomorrow. It’s game time!”

Nutter, national political chair for the campaign, won’t say what he’s paid for the position. But last quarter, Bloomberg’s campaign paid Nutter’s company $15,000, according to campaign finance reports. Nutter also continues to teach at Columbia University. He was set to fly back from California on Tuesday to teach his students about urban poverty and social welfare.

On Monday, he cruised between events up and down San Francisco’s hilly streets listening to the rapper CJ Smooth. At Bloomberg’s San Francisco field office, Nutter bumped forearms to greet campaign staff — coronavirus has some Californians avoiding handshakes — and posed for pictures. A former parks commissioner in New York City wanted to talk about Philadelphia green spaces. A former Villanova University student, now living in the Bay Area, told Nutter he’d campaigned for him. A TV producer thanked him on behalf of his friends whose wedding he had officiated at as mayor.

Later, as Nutter waited in the lobby of ABC7 in downtown San Francisco for a midday interview, a young man escorting a drag queen pointed at him excitedly. “Mayor Nutter!”

“Hello?” Nutter said.

Adam Scott, a Philadelphia transplant, recognized Nutter while accompanying his partner, Sakura M. Rock, a guest in an earlier segment of the same midday news show to talk about her appearance on RuPaul’s Drag Race. The two guests sat in adjacent green rooms — Nutter with his suited-up entourage and Sakura with her leotard adorned with roses and sequins. Sakura wouldn’t say who she was voting for Tuesday.

As involved as he is in national politics, Nutter won’t talk about city happenings at all. What does he think of the soda tax? No comment. Supervised injection sites? Nothing.

On the campaign trail, Nutter often finds himself defending Bloomberg. Nutter did two TV interviews Monday that lasted less than five minutes. Most of the time was spent on Bloomberg’s record on stop-and-frisk and complaints filed against his company by female former employees.

“If folks weren’t worried about us, they wouldn’t be coming at us so hard,” Nutter said of the scrutiny. “The issues are the issues, and it’s one of a number of reasons you actually don’t see a lot of mayors run for president, because we do have records and we do make some really tough decisions, and often those decisions really do potentially upset a lot of people in your hometown.

“But if you decide to run for president of the United States, everybody knows.”

Bloomberg apologized for stop-and-frisk right before launching his campaign, but the issue has dogged him in TV interviews and on debate stages.

It has also forced Nutter to reckon with his own record in Philadelphia, where he implemented a version of the policy that has fierce critics at home.

Nutter again offered an apology of sorts on Monday to “anyone who was abused, anyone who was mistreated, anyone who was intimidated, anyone who was treated inappropriately by the police."

While Biden was coming off a big win driven by African American voters, Nutter said Bloomberg could cut into that support with his plans to close the racial wealth gap by increasing black home and business ownership. Some polls showed growing support for Bloomberg among African Americans. And Nutter thinks many black voters are too practical to back Sanders.

“Some folks are out here talking about free this, free that," Nutter said. "Mike Bloomberg wants you to actually be able to buy your own way, take care of your own family. ... Black people are about economic empowerment. Most black people are not trying to be socialists.”

Bloomberg’s work fighting for gun control is something Nutter says will also appeal to African Americans. Nutter often mentions it, and in San Francisco bonded over the issue with several volunteers.

Richard Martinez, who lost his son in the 2014 Isla Vista shooting, met Nutter at the field office and showed him how his son’s watch, which Martinez still wears, stopped when he died. Nutter, in turn, showed him a picture he keeps in his wallet of 3-year-old Tynirah Borum, who was shot and killed on her Grays Ferry porch in 2014.

For now, Nutter is focused on a more national schedule, but he plans to campaign in Pennsylvania, where Bloomberg has a dozen field offices. Bloomberg may have started late, Nutter said Monday, but he has longevity. The Pennsylvania primary is April 28.

“While everyone else was focused on Iowa, New Hampshire, Nevada, South Carolina — they land, pack up and go." Nutter said. “We land in places like California, Texas, and Pennsylvania and Wisconsinm and we don’t leave."