More than 30 years ago, a Baptist television star had a vision.

Pat Robertson imagined a nation where conservative Christian values reigned in the halls of power. Abortion would be illegal. Prayer would be restored to public schools. Crosses would be prominently displayed in city halls and courthouses. Conservative Christian believers would no longer be ignored, as he felt they were.

Mr. Robertson ran for president in 1988, hoping to channel evangelistic popularity from his growing television empire, the Christian Broadcasting Network, into Republican political might. Ultimately he failed — even devout Christians worried about the intensity with which the celebrity minister blended church and state.

And yet, by the time of his death on Thursday, the vision he championed had gained more power than he could have ever thought possible. The alliance between evangelical Christianity and Republican politics has fused, even as America has grown increasingly secular. The polarizing rhetoric of his often inflammatory views has become a defining feature of American politics.

Mr. Robertson lived to see the Supreme Court overturn the right to abortion established by Roe v. Wade, a president move the United States Embassy in Israel to Jerusalem, and an entire mass of conservative Christian voters resist what they felt was their declining place in American life by electing Donald J. Trump, a man who promised to restore their power.

“He saw the Republican Party, as we do today, as being the party that is most in line with the Judeo-Christian values,” said Bob Vander Plaats, president of the Family Leader in Iowa. “The party is not going to save us, but the party may be a vehicle where we can influence and influence change.”

Former President Trump — like Mr. Robertson, a popular television star with widespread grass-roots appeal — tested just how far the merger could go.

Mr. Robertson came to prominence as an uncompromising figure. He asserted that the Sept. 11, 2001, terrorist attacks were God’s punishment for homosexuality and secularism and suggested that natural disasters were divine retribution for abortion. He made compromises of his own when necessary: Weeks before the 2016 election, he defended Mr. Trump after a video revealed him making vulgar comments about women.

Mr. Robertson deserves credit for creating infrastructure for the modern-day Christian conservative movement, from his media empire to his establishment of a Christian university and the way he “changed the face of evangelical Christianity with respect to Israel,” said Rick Santorum, former Republican senator from Pennsylvania and presidential candidate.

Despite conservative Christianity’s political successes, its influence in culture is far less assured. And Mr. Robertson has left a mixed legacy.

Some younger conservative Christians now balk at the very idea of such a close marriage between religion and politics, arguing that politics is a corrupting force in spiritual matters.

Other conservative Christians, like Mr. Santorum, still feel that much of Mr. Robertson’s vision remains to be achieved, particularly as many Americans accept rapidly changing attitudes toward sexuality and gender.

“We’ve been miserable failures,” Mr. Santorum said of the religious right and its place in the culture wars. “The country has continued to dramatically change.”

The Christian Coalition that Mr. Robertson founded to harness evangelical fervor for political gain found success in the early 1990s before losing prominence to organizations that took up similar missions.

Still, Mr. Robertson’s work spawned many of today’s conservative evangelical political players, who worked to cement the alliance between evangelical voters and Mr. Trump.

Ralph Reed, whom Mr. Robertson tapped to lead the Christian Coalition, guides presidential contenders on how to win the evangelical base. Tony Perkins of the Family Research Council, a conservative think tank and lobbying group, credited Mr. Robertson for “vision and courage” that shaped his own introduction to political action.

Republican politicians have come to see Christian media, which Mr. Robertson pioneered, as a powerful tool for their ambitions and agendas. As Mr. Trump railed against “fake news,” he would frequently give interviews to the Christian Broadcasting Network’s David Brody. Mike Pence turned to the network to shore up base support after White House crises, like revelations about Mr. Trump and a $130,000 payment to a pornographic film actress.

Mike Huckabee, a former Arkansas governor who ran for president, dished out political commentary on his own show on Trinity Broadcasting Network, started to rival Christian Broadcasting Network’s success.

Mr. Robertson’s institutions came to shape the legal landscape of the Trump era. Regent University, the school he founded in Virginia Beach, started a law school that now feeds many judicial clerkships, reflecting the tightening conservative grip on the country’s judicial system. One of Mr. Trump’s lead lawyers in his first impeachment trial was Jay Sekulow, chief counsel of the American Center for Law and Justice, which Mr. Robertson founded in part to push back against the American Civil Liberties Union.

Mr. Robertson, with allies like Jerry Falwell Sr. of Liberty University, saw early on how Christians could use television to reach new audiences. He revolutionized evangelical communication, both by showing the broader political world how large and potent the Christian community was, and by teaching Christians how to use new technologies to their cultural advantage.

In the 1970s, his television network saw itself as part of a “new charismatic renewal movement,” which had yet to go mainstream in America. The network produced myriad shows and programs to shape how evangelical communities across the country should respond to the world around them.

“They see what’s going on in the culture from a Christian worldview, and that helps people understand how they get involved, not only maybe on national politics, but particularly on local,” said Troy Miller, chief executive officer of National Religious Broadcasters.

Mr. Trump rose to power with early backing from prominent charismatic televangelists, many of whom built businesses that emerged from the strength of Robertson’s Christian television legacy, signaling a new moment of political maturity for that brand of Christianity in American public life.

The fate of the empire Mr. Robertson helped to build remains an open question.

Many young evangelicals are increasingly frustrated with that political alliance, and with the moral failures of previous Christian generations on issues like sexual abuse, said Karen Swallow Prior, a professor at Southeastern Baptist Theological Seminary. Some are seeking reform, using social media tools of their own day to push back against the politicization of religious faith, even as conservative Christian institutions try to double down on their political might.

“What we are seeing now is the younger generations of Christians who are using their technology to break open the cracks in the foundation of what they built,” Ms. Swallow Prior said.