AUSTIN, Texas — Republican lawmakers passed a bill that would give Texas some of the nation’s most restrictive abortion laws and force most of its clinics to close, leading Democrats to promise a fight over the contentious measure in the courts at the ballot box.

More than 2,000 demonstrators filled the Capitol building in Austin to voice their opposition to the bill, including six protesters who were dragged out of the Senate chamber by state troopers for trying to disrupt the debate. The Republican majority passed the bill unchanged just before midnight, with all but one Democrat voting against it.

“Today the Texas Legislature took its final step in our historic effort to protect life,” said Gov. Rick Perry, who will sign the bill into law in the next few days. “This legislation builds on the strong and unwavering commitment we have made to defend life and protect women’s health.”

Democrats promised a legal challenge to the measure, which will ban abortions after 20 weeks, require doctors who perform abortions to have admitting privileges at a nearby hospital and require all abortions to take place in surgical centers. Only five out of Texas’ 42 existing abortion clinics meet the requirements to be a surgical center, and clinic owners say they can’t afford to upgrade or relocate.

“There will be a lawsuit. I promise you,” Dallas Sen. Royce West said on the Senate floor, raising his right hand as if taking an oath.

Democrats proposed 20 amendments to the bill, including making exceptions in cases of rape and incest and allowing doctors more leeway in prescribing abortion-inducing drugs. But Republicans would have none of it.

The bill is one of many championed in Republican-led states this year by anti-abortion groups set on challenging the U.S. Supreme Court’s Roe v. Wade ruling, which established a woman’s right to get an abortion until the point in which a fetus could viably survive outside the womb. A fetus is generally considered viable at 22 to 24 weeks.

Texas falls under the 5th Circuit Court of Appeals, which has shown a willingness to accept more stringent limits on abortions.

By passing the new restrictions, Republicans pleased the Christian conservatives who make up the majority of primary voters. But they inspired abortion rights supporters to protest at the state Capitol in numbers not seen in Texas in at least 20 years.

Demonstrators packed normally boring committee hearings to voice their anger over the abortion bill and managed to disrupt key votes. They finished a lengthy filibuster by Democratic Sen. Wendy Davis, of Fort Worth, by jeering for the last 15 minutes of the first special legislative session, effectively killing the bill.

That’s when Perry called lawmakers back for round two. But opponents said the fight is far from over and used the popular anger to register and organize Democratic voters.

“Let’s make sure that tonight is not an ending point, it’s a beginning point for our future, our collective futures, as we work to take this state back.” Davis told 2,000 adoring supporters after the bill passed.

The Texas Republican Party, meanwhile, celebrated what they consider to be a major victory that makes Texas “a nationwide leader in pro-life legislation.”

“As Democrats continue to talk about their dreams of turning Texas blue, passage of (the bill) is proof that Texans are conservative and organized and we look forward to working with our amazing Republican leadership in the Texas Legislature as they finish the special session strong,” a party statement said.

Friday’s debate took place before a packed gallery of demonstrators, with anti-abortion activists wearing blue and abortion-rights supporters wearing orange. Security was tight, and state troopers reported confiscating bottles of urine and feces as they worked to prevent another attempt to stop the Republican majority from passing the proposal.