Houston, the fourth most populous city in the nation, is an old, bloody battleground for gays, something that has only intensified since it thrice elected lesbian Democrat Annise Parker as its mayor. But even as voters prepare to elect Parker’s successor November 3, the battle continues. And that’s why a comprehensive human rights ordinance to prohibit discrimination against a wide range of minorities in a wide range of places is focused squarely on its application to LGBT people and public bathrooms.

A “Yes” vote on Proposition 1 retains the Houston Equal Rights Ordinance (HERO); a “No” vote repeals it. Local television station KHOU reported Monday that “early voting” (allowed from October 19-30) has already seen heavy turnouts, nothing that between 17 percent and 20 percent “are not regular voters.” A KPRC 2 News poll October 12-14 found 45 percent would vote “Yes,” 36 percent “No,” 20 percent undecided, with a margin of error of plus-or-minus 4.5 percent. Most of those undecided voters, said a local university political science professor, will likely vote “No.”

In some ways, a close vote –even one that repeals the ordinance– could be seen as an improvement for Houston. In 1985, city voters rejected an effort to prohibit sexual orientation discrimination by a margin of four to one. And that ballot measure didn’t include the word “gay” and covered only city employment. In 2001, 52 percent of Houston voters amended the city charter to prohibit any “privilege” based on sexual orientation and to deny domestic partners of city employees the benefits provided to the spouses of married city employees.

Things changed dramatically two years later, when Houston elected a long-time lesbian Democratic activist, Annise Parker, as mayor, then re-elected her twice. After the U.S. Supreme Court ruled in U.S. v. Windsor that the federal government could not deny recognition to marriage licenses obtained by same-sex couples, Mayor Parker implemented a policy of providing equal benefits to Houston city employees who had gone to other states and obtained marriage licenses with their same-sex partners.

But opposition quickly mounted, and Parker responded by persuading the city council to hold public hearings. Ultimately, in May 2014, the Council passed a much more comprehensive law –the Houston Equal Rights Ordinance (HERO)— to prohibit discrimination in both the public and private sector employment, housing, and public accommodations based on “sex, race, color, ethnicity, national origin, age, familial status, marital status, religion, disability, sexual orientation, genetic information, gender identity, or pregnancy.”

For opponents, it’s all about gender identity and public accommodations:

The Campaign for Houston website calls HERO “The Bathroom Ordinance” and warns it will enable men to claim to be women to enter ladies’ restrooms. And its latest ad, in grainy black and white, shows a young girl going into a women’s restroom and entering a stall. As she does, a man dressed in men’s clothing, exits the stall next to hers and steps inside the stall where the girl is standing.

Supporters of the ordinance have tackled the bathroom argument head-on. One video ad shows a retired Houston police officer “and father of four girls” telling viewers, “It’s already illegal for men to go into women’s restrooms to harass or harm someone.” Plus, they’ve come up with their own powerful argument: If Houston repeals this ordinance, the city could lose opportunities to attract major employers and host big events, like the Super Bowl.

A vice president for the Dow Chemical Company, which employs 13,000 people in the Houston area, wrote an editorial saying the HERO ordinance is “necessary to keep attracting top-notch talent….”

Even the White House has gotten involved. White House spokesman Jeff Tiller issued a statement Thursday saying, “the President and Vice President have been strong supporters of state and local efforts to protect Americans from being discriminated against based on who they are and who they love. We’re confident that the citizens of Houston will vote in favor of fairness and equality.”