The Senate gallery in the Capitol in Austin, Tex. Business interests oppose a restrictive bathroom bill, fearful of repeating North Carolina’s experience.

AUSTIN, Tex. — With little more than a week left in Texas’ 30-day special legislative session, a barrage of corporate advertising and activism is threatening to sink legislation restricting transgender bathroom use that has been a flash point in the state’s culture wars.

Social conservatives and the state’s powerful lieutenant governor, Dan Patrick, have backed the effort. Gay rights groups, business groups and the House speaker, Joe Straus, one of the few powerful moderate voices in the Texas Legislature, have opposed it. But after the State Senate, where Mr. Patrick presides, passed a bill, a narrower one is showing few signs of life in the 150-member House.

The effort is now focused on the House version, but State Representative Jonathan Stickland, one of the bill’s 46 co-authors and a member of the Tea Party-backed Freedom Caucus, said he was pessimistic about its chances of being allowed to advance to a vote.

“I think the Straus team has already decided that they are not going to let it out,” said Mr. Stickland, who, like other members of the staunchly conservative caucus, persistently defies the speaker’s leadership. “This is clearly part of a national agenda that is being pushed by the progressive left, and I think that that is just all coming to a head here.”

The Senate bill would require transgender people to use bathrooms in schools and local government buildings corresponding to the gender listed on their birth certificates or state-issued identification cards. The House bill would prevent school districts and county or local governments from adopting or enforcing nondiscrimination ordinances that would allow transgender people to use bathrooms of their choice. The ordinance override provision is also an element in the Senate bill.

Although law enforcement, religious groups and transgender advocates have all been part of the opposing coalition, big business has been a dominant force throughout the debate.

“Corporate America is stepping forward, speaking loudly about the fact that this will have a chilling effect on business opportunity in this state,” said State Representative Byron Cook, a Republican and the chairman of the House State Affairs Committee, who has thus far refused to call a hearing on the bill. “I’m hearing from many major corporations about this bill and…