SAN FRANCISCO — Speaking to a packed crowd of supporters on Monday evening, Sen. Bernie Sanders, I-Vt., said he was still mulling entering the 2016 presidential contest, but would only do so if he thought he could “put together millions of people who are prepared to work really hard to take on the big-money interests."

Sanders has openly discussed his potential candidacy for months, and even paid a visit to the crucial primary state of Iowa earlier this year. But in recent weeks he has begun to sound more reluctant about jumping into the race, in large part because of doubts over whether he could raise the money necessary to run a credible campaign. During Monday’s speaking event, Sanders indicated that he was concerned a poor showing would undermine political support for left-wing economic policies.

“It has to be done well,” the Senate’s one self-identified democratic socialist said during a public event at San Francisco's Commonwealth Club, the oldest public-affairs forum in the United States. “Because if it’s not done well, then people will say, ‘Oh, income and wealth inequality: If you didn’t do very well in your campaign, then no one believes in that.’"

But if the senator is leaning against running, he gave no indication on Monday. Instead he turned the question on the audience, asking how many people in the crowd wanted him to run for president and would be willing to volunteer for his campaign if he did.

“Are people of the belief that we really cannot defeat these guys because they’re so powerful?” he asked, referring to the billionaires who he says he would be running to oppose. “Or in fact is there enough hope left in America to bring out people together to fight for a different country?"

When people in the audience began to applaud in response, he waved it off. “No, it was a question, not a comment,” he said.

The audience — mostly residents of one of the most liberal regions of the country — seemed overwhelmingly supportive of a presidential bid. When Sanders asked again near the end of the event how many people in the audience believe he should run for president, he received nearly unanimous applause.

If doubts about his ability to raise money are the main thing giving Sanders pause, then California’s Bay Area is an ideal place to put those doubts to the test. The region is a hot spot for Democratic political fundraising. Hillary Clinton, the presumptive frontrunner in the Democratic primary, made a recent appearance in nearby Silicon Valley and is expected to make a few more in April.

Much of the rest of Sanders’s appearance was dedicated to his key policy themes: Rising inequality, stagnating wages, public investment, and the people who he jokingly referred to as “my good friends on Wall Street."

In response to one question about financial regulation, Sanders endorsed “a fee on Wall Street speculation” — an apparent reference to the idea of a financial transaction tax — and urged government action to “break up” the large financial institutions that are considered “too big to fail."

“Now having said that, David,” he said, addressing moderator David Campos, a member of San Francisco’s Board of Supervisors, “do you think I’m going to get many campaign contributions?"