The ordinance had banned discrimination on the basis of sexual orientation, gender identity, and 11 other characteristics in employment, housing, and public accommodation. But anti-LGBT forces rallied, including the lieutenant governor and a veteran antigay activist doctor from Houston, to repeal the measure, which the City Council passed in 2014.
With about 95 percent of votes counted, the ordinance was losing 61 percent to 39 percent, according to the Chronicle.
The opposition painted the law as a "bathroom bill" by preying on fears of transgender people, claiming that men would invade women's restrooms to assault them; such behavior has never been reported as a result of a trans-inclusive equal rights ordinance.
"Prop. 1 is not about equality. That's already the law," said Lt. Gov. Dan Patrick in a video posted as part of the campaign to Vote NO. "It's about letting men in women's locker rooms and bathrooms."
On the other side of the fight, the ordinance had received public support from President Obama, Hillary Clinton, and Bernie Sanders. It also got the backing of nearly 60 companies — including Apple, General Electric, Hewlett Packard, BASF, and EMC.
It's a blow specifically to the city's out mayor, Annise Parker. She had pressed for the law and was then sued when its detractors pushed to get the repeal placed on the ballot. The Texas Supreme Court ruled in July that Houston officials either had to repeal HERO or put it up for a vote by the public.
Human Rights Campaign president Chad Griffin noted that Houston becomes the largest American city without protection from discrimination for LGBT citizens, and he warned that opponents of equality will try to expand on their success in other parts of the country.
"It's almost unbelievable that this could happen in a city like Houston, but make no mistake: if we don't double down today, we'll face the same thing again and again in cities across the nation," said Griffin in an email to HRC supporters.
The coalition formed to fight for the ordinance, Houston Unites, said Tuesday that it would press to have it restored.
"We are gravely disappointed that for now, Houstonians will continue to be denied critical local protections against discrimination," the group said in a statement on its Facebook page, adding later that "Tonight is not the end."
Watch an example of the video campaign run against HERO: