A rally in Boston shows support for a Massachusetts law protecting transgender people from discrimination in public places. (Karen Weintraub for The Washington Post)

With the country’s first statewide referendum on transgender rights just days away, a crowd armed with rainbow flags descended on Boston’s City Hall Plaza over the weekend. They cheered on those who declared their transgender status and spoke of the importance of combating hate with love.

“Trans rights are human rights,” they shouted.

At stake is a two-year-old Massachusetts law protecting transgender people from discrimination in public places, including restaurants, stores, hospitals, libraries and gyms. Opponents say it puts women at risk in public restrooms. Backers say it is essential to support and recognize transgender people.

The ballot question took on even more significance after news broke last week that the Trump administration is considering a revised definition of gender under federal civil rights law, one that would specify sex as either male or female, determined by genitalia at birth and unchangeable. Such a definition would remove key legal protections for transgender people.

Many participants in Sunday’s rally said they were there because they are transgender or have transgender friends or family members.

Renee Manning of Andover, Mass., said she had spent decades feeling alone as a transgender person. The size of the crowd — which police estimated at 1,200 to 1,500 people — filled her with hope, she said.

“I’ve seen the worst of humanity. I’ve also seen the best,” Manning said, pointing around her. “The fact that these people care that I exist is mind-boggling.”

Yet others came specifically because they are not trans. Ken Pope of the Boston neighborhood Jamaica Plain, who plays, fixes and sells French horns, attended with his wife and adult daughter.

“I think it’s important for people like me to be here,” he said, “to show how silly it is to fear other people’s choices that have no effect on them.”

Polls have shown support for the law runs high in Massachusetts, a state that is considered liberal despite consistently electing Republican governors. Gov. Charlie Baker (R) signed the bill into law and said in an op-ed this month he supports keeping it in place.

“I’m hoping, if we can win by a huge margin, that the U.S. will follow our lead,” said Kelsey Barowich of the Dorchester neighborhood. Barowich is a worker on the “Yes on 3” campaign, which has raised more than $4 million, including nearly $1 million from businesses, a campaign spokeswoman said.

According to pollster Steve Koczela, social conservatives wanted a referendum on the ballot Tuesday to gauge support for transgender rights. Weak support here would send a message to the rest of the country: “If Massachusetts would be open to overturning it, then anywhere would,” said Koczela, president of MassINC, an independent polling firm in Boston.

But the “yes” camp has a commanding lead in public opinion. In a September survey by Koczela’s firm, 71 percent of respondents said they support keeping the law in place, while 21 percent want to repeal it with a “no” vote.

The Suffolk University Political Research Center released survey results Monday showing that 68 percent planned to vote yes and 28 percent no. In an earlier poll, the same group found supporters were ahead in every demographic group examined.

Director David Paleologos said women are more likely than men to favor upholding the law despite opponents positioning the measure as being about women’s safety. Sixty-three percent of men favor keeping the law compared with 81 percent of women.

The “no” campaign, which goes by Keep MA Safe online and often refers to the ballot initiative as the “bathroom and locker room law,” has run a 30-second television spot showing a young woman being stalked in a dressing room by a sex offender. Spokeswoman Yvette Ollada said the current statute does not provide enough protections for women in bathrooms and needs to be revised rather than reaffirmed. She said her group’s aim is not to deprive anyone of their rights — which are protected under other laws — or to serve as a national referendum on transgender rights.

“We aren’t saying repeal this law and do nothing. We’re saying repeal this law and go back to the drawing board, because this law is bad,” she said.

Keep MA Safe has raised about $450,000 since 2016.

Recent research does not bear out opponents’ fears. A study published in September by the Williams Institute at UCLA School of Law found crimes did not go up when the Massachusetts “public accommodations” statute took effect.

Before the law, some local communities had protections for transgender people in public places, while others did not. Lead researcher Amira Hasenbush compared bathroom safety in both.

“The study found there was no empirical reality” to fears that the law would make public bathrooms less safe, she said. “There didn’t seem to be any impact on privacy or public safety.”