Twenty years ago, the Republican Party started what may have been the most lifesaving government initiative in modern history. It turned the tide of AIDS around the world and has saved 25 million lives so far — equivalent to the entire population of Australia.

So it’s a reflection of the madness that has infected the Republican Party that today some conservatives are repudiating perhaps the best thing they ever did, battling the reauthorization of this program.

PEPFAR, which stands for the President’s Emergency Plan for AIDS Relief, has a legislative authorization that expires at the end of this month. And Republicans are now fighting that reauthorization.

Republicans should be extraordinarily proud of their boldness in crafting PEPFAR, which provides antiretroviral medicines to AIDS patients and operates in more than 50 countries.

The devastation of AIDS in the 1990s and 2000s, particularly in southern Africa, may be difficult for people today to understand. Intimacy became lethal. Estimates circulated that AIDS would kill 100 million people over the next 20 years.

PEPFAR changed all that. It brought AIDS under control and gave countries their futures back.

The assault on PEPFAR accelerated in May with a report by the conservative Heritage Foundation warning without evidence that the Biden administration was using the program to promote a “radical social agenda” — including liberalized abortions.

Conservative critics, seeing a crusade forming, rushed to join. They noted that some PEPFAR dollars have gone to nonprofits that also, using separate resources, support abortions. That’s true. But longstanding American policy ensures that the accounts are separate and the U.S. dollars don’t pay for abortions. There’s nothing new here, and it’s particularly galling that Republicans preen as “pro-life” for attacking a program that saves lives on a scale like nothing before or since.

Unfortunately, some conservative organizations have said that in their political scorecards rating members of Congress they will count a vote to reauthorize PEPFAR in its present form as a vote for abortion rights. That makes it toxic for many Republican members of Congress who fear that they might no longer have a perfect “pro-life” record.

The Heritage Foundation critique also argued that AIDS is primarily a “lifestyle disease” and so “should be suppressed through education, moral suasion and legal sanctions” rather than medication. That phrase reeks of sanctimony. During the worst of the epidemic, I met Zambian women whose husbands were away working as miners; the women were terrified that when their husbands, whom they loved, came home on vacations, they would have to sleep with them — and risk death if their husbands had strayed.

The most dangerous thing a woman there could do, it was said then, was to get married. If American conservatives want to fight AIDS with finger wagging instead of antiretrovirals, those women will again be at great risk.

This crisis over reauthorization has to do with the fever that has beset elements of the G.O.P., leaving some senators and House members inhabiting what seems to be delirium. A P.R.R.I. poll in 2021 found that 23 percent of Republicans agree that “The government, media and financial worlds in the U.S. are controlled by a group of Satan-worshipping pedophiles who run a global child sex-trafficking operation.” Even now, some two-thirds of Republicans believe that President Biden was not legitimately elected. Only 40 percent of Republicans say that the benefits of Covid vaccines outweigh the risks (which is why research suggests that Covid may have disproportionately killed Republicans).

Republican critics say that they’re still for PEPFAR in principle, but only if there are changes or a shorter reauthorization period, which would undermine confidence in the program — think of it as death by 1,000 cuts. If PEPFAR is not reauthorized by its expiry at the end of this month, it would still continue if Congress separately appropriates further funding for it, but in hobbled form.

The denunciations of PEPFAR horrify the Republican Party’s grown-ups, who recognize how important the program has been.

“This is America at its best,” Condoleezza Rice, President George W. Bush’s national security adviser and secretary of state, told me.

“Let’s not throw away one of the really great moments when the United States took on this extraordinary challenge of people who were dying from this pandemic and intervened and started to save lives,” Rice said. “I just don’t understand why we wouldn’t want to continue to do that.”

PEPFAR is one reason polls show that Africa is one of the most pro-American parts of the globe. China is competing for hearts and minds there, and America’s struggle to reauthorize PEPFAR amounts to a gift to Xi Jinping.

Early this year, I chided Democrats for failing to acknowledge Bush’s heroism in creating PEPFAR. I wrote that column because we all have cognitive biases that nudge us toward self-congratulatory narratives in which our own side is virtuously battling idiots on the other side. PEPFAR reminds us of the complicated truth, which is that in 2003, Bush both began a catastrophic war that killed hundreds of thousands of people and also started a program that saved 25 million lives.

Does that mess with our heads? Of course. But that’s not necessarily a bad thing. The ability to navigate a messy, contradictory world is a mark of maturity — and of governing.

Now it’s Republicans who need to muster the maturity to govern. And in that sense PEPFAR’s reauthorization is a test for a once great political party that now sometimes seems to be fighting psychosis.