Houston, the last major US city to pass LGBT protections, is now likely to be the site of the most expensive battle in history over a local nondiscrimination ordinance.

Both sides launched their campaigns last week in the ballot fight over the Houston Equal Rights Ordinance (HERO), which voters will decide Nov. 3. And both say they'll need to spend $2 million to win. Voters are currently split on whether to repeal the ordinance, with roughly one-third undecided. Project Q Houston reports:

Last week, a coalition of progressive groups launched a campaign to uphold the ordinance, which will appear on the Nov. 3 ballot. The Houston Unites campaign is led by the ACLU of Texas, Equality Texas, Freedom For All Americans, the Human Rights Campaign, the NAACP Houston Branch and the Texas Freedom Network. In addition to sexual orientation and gender identity, the ordinance prohibits discrimination based on 13 other characteristics, including race. …

HERO opponents informally kicked off their campaign to repeal the ordinance at an anti-LGBT rally last week that also marked the launch of an eight-city “Faith Family Freedom Tour.” Steven Hotze (right), lead sponsor of the tour, wielded a sword on stage, compared gay people to Nazis and pledged to drive “homofascists” and their “satanic cults” out of Houston and back to San Francisco. The rally, held in a half-full ballroom at the Hilton Post Oak at the Galleria, concluded with a money beg for Hotze's group, the Conservative Republicans of Texas.

After the City Council in the nation's fourth-largest city approved the ordinance in May 2014, opponents submitted a petition seeking to repeal it. The city rejected the petition, saying it didn't have enough valid signatures, prompting opponents to file a lawsuit. A district judge upheld the city's decision, saying the petition contained widespread forgery, but the all-Republican Texas Supreme Court later ruled Houston council members had to either repeal the ordinance or place it on the ballot.

The Houston Chronicle has more on the strategy behind the dueling campaigns:

Opponents will push a public safety campaign driven by the perceived threat that male sexual predators dressed in drag will use the law as cover to enter women's restrooms. Supporters, meanwhile, will seek to debunk that and warn that repealing the law would irreparably harm the city's image.

Both groups said they will need to spend at least $2 million to pepper voters with targeted direct mail and a few choice ads. …

The challenge for supporters is to fend off the public safety allegations without losing their own message, University of Houston political scientist Brandon Rottinghaus said. The business angle – that events such as the Super Bowl and Final Four could go elsewhere in the event of repeal – likely will factor into supporters' argument, he said.

In addition to hosting the Final Four in 2016 and the Super Bowl in 2017, Houston is home to several Fortune 500 companies with high scores on the Human Rights Campaign's Corporate Equality Index. Thus far, however, none has spoken out publicly in favor of the ordinance. Houston-based Fortune 500 companies include BP America (CEI Score: 90), ConocoPhillips (75), Marathon Oil Corp. (75), Shell Oil Co. (95), Spectra Energy Corp. (90) and Waste Management Inc. (90).

Watch a report on the launch of Houston Unites, the campaign in support of the ordinance, below.