Over four days that summer, the women filed into a law office in Baton Rouge, La., to share their stories with the unassuming associate just a year out of law school. Floors at the abortion clinic where they worked, they told him, were flecked with dried blood. The surgical instruments were so rusted they left orange streaks on your hand. Patients screamed in pain as brusque doctors performed their abortions. Some women were carried to their cars still woozy from sedation.

For many people in Louisiana, the allegations against the Delta Clinic of Baton Rouge were a grim confirmation of what they already suspected. For the young lawyer, the case was also an opportunity.

Still in his 20s, Mike Johnson was already a rising star in Louisiana’s anti-abortion movement. His firm’s lawsuit against Delta, filed in late 1998 on behalf of a patient, alleging that an abortion there had left her injured and infected, set off a furor. Aided by Mr. Johnson, a local TV news investigation would lead Louisiana’s Republican governor to declare a public health emergency. It was Mr. Johnson’s first triumph in a grinding two-decade battle against the Delta clinic — and against abortion more broadly — that would become one of the animating crusades of his public life.

“I think the Delta clinic was the pivot point for Mike,” said Gene Mills, president of Louisiana Family Forum, an influential conservative group. “He was interested and involved, but when that evidence came forward, he stepped in and got that information out to the government.”

The Delta case not only thrust Mr. Johnson to the center of the abortion battles raging throughout the South. It set in motion the career that would ultimately bring him to the U.S. House of Representatives, where he was elected speaker last month with the unanimous support of exhausted, divided Republican lawmakers. In the intervening years, as a lawyer and politician, Mr. Johnson played an influential behind-the-scenes role in national efforts to reassert religious values in the public square, fighting to defend school prayer and resist the expansion of gay rights while whittling away access to abortion.

Now, for the first time in history, modern-day Christian conservatives have in the speaker’s office not merely a reliable ally, but one of their own most dogged foot soldiers.

“He’s the most conservative speaker that we’ve seen in modern times — probably ever,” said Tony Perkins, a fellow Louisianian who is president of the Washington-based Family Research Council and who, as a state lawmaker two decades ago, worked closely with Mr. Johnson. “I passed a lot of legislation on these issues, a lot of it got struck down,” he added. “Now the stuff is making it through the courts, and it’s in large part because of litigation from attorneys like Mike.”

Mr. Johnson declined to be interviewed for this article. But allies and opponents alike described him in interviews as someone who believed that the culture wars could be won by attrition, through incremental legislative and legal resistance. For years after the Delta controversy, Mr. Johnson helped draft and defend successive Louisiana laws aimed at tightly regulating abortion providers, helping make abortion increasingly inaccessible in the state even as the procedure remained technically legal.

Last year, lawyers for the Alliance Defending Freedom, the Christian legal-advocacy group where Mr. Johnson worked for roughly a decade, achieved conservatives’ longest-sought victory in the abortion wars: persuading the Supreme Court’s newly enlarged conservative majority to overturn Roe v. Wade — and allowing states like Louisiana to largely outlaw abortion.

Mr. Johnson’s ascent to the speakership comes as Republicans grapple with the ensuing backlash. Energized by anger among liberals and many swing voters in the 2022 elections, Democrats are seeking to make abortion rights the centerpiece of the upcoming presidential campaign, hoping at the same time to vanquish Mr. Johnson’s shaky Republican majority in the House next fall. Last Tuesday, Democrats exploited voter anger over threats to abortion rights to win off-year victories stretching from the battleground states of Virginia and Pennsylvania to Republican strongholds like Ohio and Kentucky.

“He has been at the forefront of the religious right movement for a long time,” said Marjorie Esman, a former head of the American Civil Liberties Union’s Louisiana chapter and an early sparring partner of Mr. Johnson. “And that movement is now, obviously, somewhat ascendant. In that sense, his larger impact starts now.”

‘The Path God Had Planned’

Even before he graduated from Louisiana State University’s law school in 1998, the future speaker had enmeshed himself in a world of influential older conservative figures, in a state that would ripple with clashes over the proper place of religion in public life.

As a law student, Mr. Johnson volunteered for the Louisiana Family Forum, which would emerge as a powerful lobbying force for the state’s conservative Christian pastors and congregations. He worked on the failed U.S. Senate campaign of Woody Jenkins, an anti-abortion Republican politician and Baton Rouge television station owner, and got to know Mr. Perkins, a state lawmaker at the time and a former journalist at Mr. Jenkins’s station.

Mr. Johnson’s first legal job was at the family firm of Thomas Benton, a Roman Catholic lawyer active in anti-abortion circles, who became a mentor. The two worked to help state lawmakers draft anti-abortion legislation. “They took me in as their own,” he would say of the Benton family, “and helped set me on the path God had planned long before.”

In 1998, the firm took on the case of a young woman named Roxie Daniels. She and her mother, Jane Stelly, alleged that an unsuccessful abortion at Delta had led to a dangerous infection, requiring hospitalization and an emergency hysterectomy.

The mother and daughter sued Delta over the botched abortion. They filed a separate suit against a hospital where Ms. Daniels was subsequently treated, seeking damages for the “wrongful death of her unborn child,” according to a complaint.

The Baton Rouge clinic was already a lightning rod for anti-abortion activists. The clinic was firebombed in 1985 and subsequently targeted by protests that led to hundreds of arrests. Though Delta faced repeated allegations of substandard care and dangerous conditions, the clinic continued to operate.

The Daniels case would be different. Bolstered by testimonials from former employees, Mr. Johnson and his allies would cast Delta as a stand-in for all abortion providers — a demonstration that “the very phrase ‘abortion care’ is an oxymoron,” as Mr. Johnson put it on his podcast last year.

An employee of the hospital where Ms. Daniels was being treated urged Ms. Stelly to call Mr. Benton and Mr. Johnson for help, advising that they were “Christians, both of them, and they are so against abortion clinics,” Ms. Stelly recalled in an interview. The lawyers soon drove to the hospital to see her, and later took her to church and arranged for her speak at a political rally.

“The lawyers came into my life and things changed a lot,” she said.

Within weeks of filing the case, Mr. Johnson arranged for Ms. Daniels and Ms. Stelly to be interviewed on Baton Rouge’s Channel 9, their identities concealed, as in the Delta lawsuit. Louisiana’s state capital was a small world: The reporter, Julie Baxter, had once worked with Mr. Perkins during his television career. A clinic worker who saw the broadcast subsequently contacted the Benton firm, according to Ms. Stelly.

“She was going to quit right then,” Ms. Stelly recalled, but the lawyers “asked her not to quit right this minute.” Instead, the worker let Ms. Baxter and a photographer into Delta after hours. In a bombshell follow-up segment, Ms. Baxter aired grainy pictures from inside Delta: filthy surgical hoses, rusted dilators, a recovery room stained with dried blood.

Though Ms. Daniels was not identified in the Delta lawsuit, which remains under seal, video posted online indicates that she later participated in follow-up interview with Ms. Baxter that named her and showed her face; the hospital lawsuit was also filed under Ms. Daniels’s real name. Efforts to reach her were unsuccessful.

Ms. Baxter, who now goes by Julie Baxter Payer, said she was “following the facts as they were.” She added, “The whole issue was, how do you regulate abortions without creating an impediment to women seeking abortions?”

The pictures caused a sensation in Baton Rouge. Yet a surprise inspection ordered by Louisiana’s governor found no cause for action. The Daniels lawsuit bounced around Louisiana courts for at least a decade, according to Yigal Bander, a lawyer for Delta at the time. It is unclear how the case was resolved, though Mr. Bander did not recall any judgment or settlement against the clinic.

“They weren’t really interested in the case,” Mr. Bander said of the Benton lawyers. “They were interested in making a big splash” and “making the government harass Delta.”

Mr. Johnson swung into action. He asked Mr. Perkins to sponsor a new bill, which he helped draft, to place abortion clinics under the same regulations as outpatient surgical centers, which typically perform more-invasive procedures. Setting aside the question of abortion’s legality, they argued, the rules were necessary to protect women. The bill not only mandated licensing and regular inspections, but imposed a host of costly new requirements, from how clinics were staffed to their layout and lighting.

It was a “very simple bill,” Mr. Perkins told his colleagues, adding that abortion clinics “have not had any form of regulation.” Some lawmakers seemed skeptical, Mr. Perkins later recalled, believing that regulating abortion clinics legitimized them. But after he played them a clip from Channel 9, the debate was over. The bill passed with little opposition.

Mr. Johnson was only getting started.

Lawsuits and Legislation

The Delta case put Mr. Johnson still a young lawyer, at the forefront of an emerging legal strategy for religious conservatives. Having failed to persuade courts to outlaw abortion, they began passing state laws that entwined clinics in a web of costly regulations, opening more doors for government investigations and private lawsuits. Abortion-rights advocates called it TRAP, for Targeted Regulation of Abortion Providers. Louisiana, where even most Democratic politicians were opposed to abortion, became “a model for other states,” as Mr. Johnson later said.

Mr. Johnson advised lawmakers on further bills aimed at imposing new rules around clinics, while mustering public pressure on state officials to investigate them.

He continued gathering sworn statements from former Delta workers, and when a state medical board placed one of the clinic’s former doctors on indefinite probation, Mr. Johnson told reporters the decision “doesn’t go far enough.”

In 2009, he wrote to Louisiana public health officials demanding a further investigation of Delta, citing its “well-documented history of dangerous noncompliance with both federal and state laws.” Health officials, bolstered by the laws Mr. Johnson had helped inspire, conducted an unannounced inspection, ultimately requiring Delta to pay a few thousand dollars in fines and address an array of code violations. That wasn’t enough for Mr. Johnson, who obtained the officials’ Delta report, then insisted that it showed they were required to shut the clinic down.

“He had a history of using legal tactics and legal arguments — sometimes kind of novel legal arguments — to go after abortion clinics,” said Michelle Erenberg, the executive director of Lift Louisiana, an organization that advocates for reproductive rights.

Though some abortion-rights defenders concede that Delta at times had health and safety issues, they saw Mr. Johnson’s attacks as part of a strategy to impose regulations so varied and extensive that clinics could not operate without generating a long list of violations, many of them minor.

Abortion opponents used the notion that there were “bad operators” to get more regulations, said Ellie Schilling, a Louisiana lawyer who worked on abortion-rights litigation against Mr. Johnson. “It was meant to be circular.”

By then, Mr. Johnson’s legal work had expanded. In 2002, he had joined the Alliance Defense Fund — renamed Alliance Defending Freedom a decade later — which opposed abortion, gay rights, and the separation of church and state. In his years with the group, Mr. Johnson was involved in more than 25 cases, racking up a mixed record. He defended “choose life” license plates and abortion-clinic protesters, filed amicus briefs against the pornography industry, and helped draw up a blueprint for cities that wanted to curtail adult clubs and video stores.

In 2015, the Supreme Court ruled that the Constitution guaranteed a right to same-sex marriage — invalidating a slew of state bans, including Louisiana’s, which Mr. Johnson had defended in court for years. In a speech to Louisiana church leaders that summer, he took an almost apocalyptic view of the ruling. “You are what’s left of Christianity in America,” he warned.

Seeing Results

By then, Mr. Johnson was defending yet another Louisiana clinic law — a battle that would prove to be abortion defenders’ last stand. The law, known as Act 620, required that abortion doctors have admitting privileges at a nearby hospital. Clinic doctors often have difficulty securing such agreements, in part because the rarity of complications from abortions means that clinics do not offer hospitals a reliable revenue stream. A nearly identical law in Texas was helping to force more than half that state’s abortion clinics out of business; abortion foes saw a similar opportunity in Louisiana, where only five abortion clinics continued to operate, among them Delta. In 2014, abortion providers sued to block the privileges law, in the case that would come to be known as June Medical Services v. Russo.

As challenges to both states’ laws wended their way through the federal courts, Mr. Johnson, by then in private practice, joined the legal team defending Louisiana’s statute, working closely with a lawyer named Kyle Duncan, a fellow Louisianian and religious-liberty advocate. Mr. Duncan — who would later be appointed to the federal appeals court for the Fifth Circuit, a font of hard-right rulings — “did all the intellectual work on the case,” recalled Ilene Jaroslaw, a New York lawyer who represented the plaintiffs in June Medical. “Mike had the connections to the various witnesses in the anti-abortion movement.”

A district court judge rejected his team’s arguments in now-familiar fashion, ruling in 2017 that the Louisiana law did not serve “any relevant credentialing function” and would “drastically burden women’s right to choose abortion.” (The Texas law was struck down in 2016.) While the June case was on appeal, Mr. Johnson, now serving in Congress, led fellow Republican lawmakers in an amicus brief.

Speaking outside the Supreme Court in March 2020, after oral arguments in the case, Mr. Johnson launched into a now-familiar litany about the Delta clinic: the “horrible abuses,” the video of rusted instruments and bloody operating tables, the workers who “testified under oath about the atrocities of what happens inside these clinics.” A 5-to-4 majority of the court was unswayed, declaring Louisiana’s Act 620 unconstitutional.

Yet just months later, the right’s broader anti-abortion campaign would come to fruition. When Justice Ruth Bader Ginsburg died in September 2020, she was replaced by Amy Coney Barrett, a reliably conservative jurist — and an old Louisiana friend of Mr. Johnson. In 2022, the court overturned Roe v. Wade.

Mr. Johnson, too, finally succeeded. In the wake of the court’s decision, after a final spasm of legal challenges, Louisiana’s last three abortion clinics, including Delta, closed their doors.

Last June, Delta’s one-story brick building in Baton Rouge was sold to anti-abortion activists.