GREENVILLE, S.C. — The Republican presidential candidates met in debate just hours after learning of the death of Supreme Court Justice Antonin Scalia. Beyond that, the debate came at a time when the entire world economy has the jitters; when yet another attempt to bring peace to Syria is in tatters; and when the Republican establishment is more nervous than ever about the continued strength of Donald Trump. And with all of that going on, the most passionate exchange of the entire event was about … relitigating the Iraq War.

It's not shocking that George W. Bush's decision to invade Iraq would come up nearly 13 years after the fact; it pops up in Democratic debates these days, too. But the exchange between Trump and Jeb Bush over Iraq Saturday night wasn't just a passing reference. It was in some ways the debate Republicans mostly didn't have back in 2004, when Democrats were consumed with the war. And here in Greenville, as has happened elsewhere in this campaign, the candidate named Bush had a hard time dealing with the subject.

The back-and-forth started when moderator John Dickerson brought up a 2008 interview with CNN in which Trump said he was surprised that Democrats had not impeached George W. Bush over the war, and that it would be "a wonderful thing" if they had.

On stage Saturday, Trump would not repeat what he said about impeachment — there are apparently limits even for Trump. But he did not hesitate to talk about Iraq. "Obviously, the war in Iraq was a big, fat mistake, all right?" Trump said. "We spent $2 trillion, thousands of lives, we don't even have it. Iran has taken over Iraq with the second-largest oil reserves in the world."

"George Bush made a mistake," Trump continued. "We can make mistakes. But that one was a beauty. We should have never been in Iraq. We have destabilized the Middle East."

And finally: "They lied," Trump said of the Bush administration. "They said there were weapons of mass destruction, there were none. And they knew there were none. There were no weapons of mass destruction."

It's not the first time Trump has said such things. But he was taking a risk, calculated or not, on saying them in South Carolina. George W. Bush remains popular among state Republicans. Perhaps that does not mean everything Bush did remains equally popular, but slamming the Republican former president so hard is a significant gamble for Trump.

On the other hand, Jeb Bush showed himself (again) unable to address Trump's basic critique.

"I am sick and tired of him going after my family," Bush said. "My dad is the greatest man alive, in my mind. And while Donald Trump was building a reality TV show, my brother was building a security apparatus to keep us safe. And I'm proud of what he did."

Bush even brought his mother into it, defending her against Trump. "Look, I won the lottery when I was born 63 years ago, looked up, and I saw my mom," Bush said. "My mom is the strongest woman I know."

The my-mom-is-great argument might not the strongest possible defense of the decision to invade Iraq. To say that Bush didn't fully engage with Trump would be an understatement.

Nor did Bush address Trump's rebuttal to the "kept us safe" claim. "The World Trade Center came down during your brother's reign, remember that," Trump said. "That's not keeping us safe."

After the debate, both sides stuck to their stories. "I think it's clear — the Iraq War was a disaster," said Trump campaign manager Corey Lewandowski. "We lost thousands of lives, spent trillions of dollars over there, and the question is, what did we get out of it?"

"I think Donald Trump's comments are ridiculous, and I think they have no place in a Republican debate," said Bush campaign manager Danny Diaz. "They totally demonstrate a total lack of seriousness, a total lack of temperament. He is demonstrating … why he is not a good nominee, why he can't be commander in chief."

Here's the issue. If George W. Bush is as popular as everyone says he is among Republicans in South Carolina, and those Republicans who approve of Bush still approve of the decision to invade Iraq — then Trump might have made some real trouble for himself Saturday night.

"In South Carolina, I don't think you're going to find an overwhelming opinion that the Iraq was a mistake," said Rep. Jeff Duncan, a supporter of Ted Cruz, after the debate.

"Trump's attack on George W. Bush will hurt him in South Carolina," added Clemson University political scientist David Woodard in an email exchange at the end of the debate. "Beyond what is said is the way it's said. Trump's manner goes to his stereotype as a bully, and it makes the viewer dislike him."

So once again, as he has so many times in this campaign, Trump has gambled. Maybe his frankness will allow other Republicans to loosen up and admit their doubts about the wisdom of the Iraq War. Or maybe he has touched the third rail of South Carolina GOP politics. He'll know more in a week.