Donald Trump, right, and Sen. Ted Cruz (R-Tex.) speak at the same time during the CBS News Republican presidential debate Saturday in Greenville, S.C. (John Bazemore/Associated Press)

Of all the surprises, of all the unexpected ironies, of all the unanticipated turns in the Republican presidential race, it’s possible that Donald Trump has been hurt by telling the truth. Trump himself must be reeling from such a development and has probably by now vowed to return to lying and bluster seasoned with personal insult — “You’re a loser” — but the fact remains that when he called the war in Iraq “a big, fat mistake,” he was exactly right. Jeb Bush, the very good brother of a very bad president, has now turned legitimate criticism of George W. Bush into an attack on his family. His family survived the war. Countless others did not.

Jeb Bush’s problem is that he has the record and the demeanor of someone who would have opposed his older brother’s invasion of Iraq. In this, he would have been no different from many other moderate Republicans — former national security adviser Brent Scowcroft , for instance — who feared we would be creating a civil war that would rip Iraq apart and entrap us for years to come. As it happened, they were right.

Trump’s problem is that he is not, in his downtime, a member of various right-wing coffee klatches where the sagacity and downright brilliance of the Iraq War are undisputed. It goes like this: Saddam Hussein is gone, his threat has been vaporized and his weapons of mass destruction, which by now he would have developed and perfected, are no longer an issue. In fact, long after Hussein was executed, I heard the late Christopher Hitchens tell members of a conservative luncheon society that Hussein’s WMD did indeed exist and would — he assured them with a nod — be found. They were buried somewhere.

Over the years, the Republican Party has been a vast incubator of foreign policy conspiracy theories. A current one has to do with Benghazi, Libya, where the Obama administration, for reasons no doubt having to do with its intrinsic evil, allowed Americans to die when, with very little effort, they could have been saved. Hillary Clinton, then the secretary of state, lied to the next of kin about why their loved ones had died — a local, spur-of-the-moment uprising instead of the terrorist attack it most certainly was. The theory ignores the muddle of the time. It is also insane.

Once, large parts of the GOP believed that a cadre of leftists and — yes — homosexuals had somehow enabled the communists to win the Chinese civil war. The charge of “Who lost China?” rang out from the halls of Congress and was supported even by Republicans who knew better. Secretary of State John Foster Dulles permitted this, allowing his department to be purged and careers ruined. A grateful nation named an airport for him.

Now we see an attempt at revision concerning the Iraq War. Trump, though, has it mostly right. It was a debacle — and it forever will remain so. It was unwise to invade, unwise to eliminate the Baath Party, unwise to eviscerate the Iraqi army — and not realistic to think anything could be done on the cheap.

Where Trump goes wrong is the implication that President Bush himself lied about what intelligence he had at the time. Others are more culpable. Vice President Dick Cheney surely exaggerated and manipulated the threat, and national security adviser Condoleezza Rice got carried away in her “mushroom cloud” description of Hussein’s nuclear potential. Hussein by then didn’t have a nuclear weapons program. As for Bush, he didn’t have a clue.

In the current campaign, with the occasional exception of John Kasich, Jeb Bush has been the only adult in the room. His answers have usually been prudent and often complicated by facts that do not lend themselves to the bumper-car format of televised debate. Possibly his finest moment occurred when he reacted with evident disgust after Trump, doing a spot-on imitation of Vlad the Impaler, enthusiastically endorsed waterboarding and “a hell of a lot worse.” Bush simply said he would not bring back waterboarding. He seemed appalled.

On Saturday, Trump started to come apart in the South Carolina debate. The truth is that he was once pro-choice and he did contribute to Democrats but he came to find the GOP more hospitable to his growing intolerance and moved right. On those issues, he has now fudged and blustered and denied the undeniable.

But on Iraq, Donald Trump has stood firm. He called the war a mistake. He may not understand. In his new political party, that’s a mistake.

Read more from Richard Cohen’s archive.