The long and loud campaign of Donald J. Trump, and now his re-election as president, have prompted deep divisions among many Chinese who advocate for democracy.

Wang Lixiong, a Beijing-based author, has been imprisoned and surveilled for his critical writings about China. The day before the election, he posted on X that Mr. Trump’s political alliance with the tech entrepreneur Elon Musk was worrying: “A Trump presidency combined with Musk’s influence may become a singularity that backfires on democracy.” People responded by condemning him, leaving hateful comments, including ones that wished him death.

Luo Yufeng, an online influencer who moved to New York more than a decade ago and posts about the possibilities that freedom brings, has also received abhorrent comments on her X account. She had been posting about her support for Mr. Trump, saying she opposed President Biden’s immigration policies.

On social media and around dinner tables, businesspeople, intellectuals and scholars I know who have fought side by side for democracy in China since the 1980s have been fighting one another over Mr. Trump. I have adopted a policy for gatherings with friends at my dining table in New York: No talk of American politics when we are eating.

I have been thinking a lot about China, democracy and Mr. Trump recently because of “Night Is Not Eternal,” a documentary by Nanfu Wang, a Chinese-born filmmaker I first met over a year ago. The film, which will debut on HBO on Nov. 19, is a moving portrayal of a Cuban activist, Rosa María Payá, who fights for democracy in her home country.

The two women met at a film festival in March 2016. Then in their 20s and early 30s, they found they were kindred spirits, having grown up under autocratic governments where speaking out was dangerous.