Dozens protest in Pelosi’s home city, where attitudes toward Taiwan are shifting.

Dozens of people gathered in downtown San Francisco on Monday to protest Speaker Nancy Pelosi’s trip to Taiwan, arguing from her home district that the visit could inflame potential war with China.

The demonstration included members of the city’s Chinese American community; the antiwar group Code Pink: Women for Peace; and the U.S.-China Peoples Friendship Association, a nonprofit group with chapters around the United States.

Julie Tang, a retired judge in San Francisco who attended the protest, called Ms. Pelosi’s trip a “very, very bad idea.”

“We are really shocked at her obstinance, that she doesn’t see the risk that she’s taking, tipping the very delicate balance between China and Taiwan,” Ms. Tang said. “It’s wholly reckless and unreasonable. It has no apparent usefulness or benefit for America or the world.”

Ms. Tang said she was a lifelong Democrat and had contributed to Ms. Pelosi’s political campaigns in the past and was now rethinking her party affiliation. Ms. Pelosi, she said, was “acting like an imperialist.”

The protest, although relatively small, seemed to reflect how attitudes toward Taiwan have changed in the city, where there are a growing number of Chinese residents, many of them born in mainland China.

In the three and a half decades that Ms. Pelosi has represented the city in Congress, connections and sympathies among her constituents have shifted decisively away from Taiwan, according to David Lee, a political science lecturer in San Francisco who specializes in voting trends of the Chinese community.

The Chinese community in San Francisco, which from the 1950s until the early 1990s was very outwardly supportive of Taiwan, today is much more connected to mainland China, partly because of immigration trends and the rise of China’s power and influence in the world, Mr. Lee said.

Ms. Pelosi’s Taiwan trip has not been a central preoccupation among Chinese Americans in San Francisco, Mr. Lee said. But among those who are actively following the issue, supporters of Taiwan appear to be a small minority. “My sense from the community is that there is more sympathy toward the mainland on this issue,” he said.