Jeb Bush wants to stop talking about past controversies. And you can see why. He has a lot to stop talking about. But let’s not honor his wish. You can learn a lot by studying recent history, and you can learn even more by watching how politicians respond to that history.

The big “Let’s move on” story of the past few days involved Mr. Bush’s response when asked in an interview whether, knowing what he knows now, he would have supported the 2003 invasion of Iraq. He answered that yes, he would. No W.M.D.? No stability after all the lives and money expended? No problem.

Then he tried to walk it back. He “interpreted the question wrong,” and isn’t interested in engaging “hypotheticals.” Anyway, “going back in time” is a “disservice” to those who served in the war.

Take a moment to savor the cowardice and vileness of that last remark. And, no, that’s not hyperbole. Mr. Bush is trying to hide behind the troops, pretending that any criticism of political leaders — especially, of course, his brother, the commander in chief — is an attack on the courage and patriotism of those who paid the price for their superiors’ mistakes. That’s sinking very low, and it tells us a lot more about the candidate’s character than any number of up-close-and-personal interviews.

Wait, there’s more: Incredibly, Mr. Bush resorted to the old passive-voice dodge, admitting only that “mistakes were made.” Indeed. By whom? Well, earlier this year Mr. Bush released a list of his chief advisers on foreign policy, and it was a who’s-who of mistake-makers, people who played essential roles in the Iraq disaster and other debacles.

Seriously, consider that list, which includes such luminaries as Paul Wolfowitz, who insisted that we would be welcomed as liberators and that the war would cost almost nothing, and Michael Chertoff, who as director of the Department of Homeland Security during Hurricane Katrina was unaware of the thousands of people stranded at the New Orleans convention center without food and water.

In Bushworld, in other words, playing a central role in catastrophic policy failure doesn’t disqualify you from future influence. If anything, a record of being disastrously wrong on national security issues seems to be a required credential.

Voters, even Republican primary voters, may not share that view, and the past few days have probably taken a toll on Mr. Bush’s presidential prospects. In a way, however, that’s unfair. Iraq is a special problem for the Bush family, which has a history both of never admitting mistakes and of sticking with loyal family retainers no matter how badly they perform. But refusal to learn from experience, combined with a version of political correctness in which you’re only acceptable if you have been wrong about crucial issues, is pervasive in the modern Republican Party.

Take my usual focus, economic policy. If you look at the list of economists who appear to have significant influence on Republican leaders, including the likely presidential candidates, you find that nearly all of them agreed, back during the “Bush boom,” that there was no housing bubble and the American economic future was bright; that nearly all of them predicted that the Federal Reserve’s efforts to fight the economic crisis that developed when that nonexistent bubble popped would lead to severe inflation; and that nearly all of them predicted that Obamacare, which went fully into effect in 2014, would be a huge job-killer.

Given how badly these predictions turned out — we had the biggest housing bust in history, inflation paranoia has been wrong for six years and counting, and 2014 delivered the best job growth since 1999 — you might think that there would be some room in the G.O.P. for economists who didn’t get everything wrong. But there isn’t. Having been completely wrong about the economy, like having been completely wrong about Iraq, seems to be a required credential.

What’s going on here? My best explanation is that we’re witnessing the effects of extreme tribalism. On the modern right, everything is a political litmus test. Anyone who tried to think through the pros and cons of the Iraq war was, by definition, an enemy of President George W. Bush and probably hated America; anyone who questioned whether the Federal Reserve was really debasing the currency was surely an enemy of capitalism and freedom.

It doesn’t matter that the skeptics have been proved right. Simply raising questions about the orthodoxies of the moment leads to excommunication, from which there is no coming back. So the only “experts” left standing are those who made all the approved mistakes. It’s kind of a fraternity of failure: men and women united by a shared history of getting everything wrong, and refusing to admit it. Will they get the chance to add more chapters to their reign of error?