There was an uninvited guest onstage Saturday night at the latest and most brutal Republican presidential debate: George W. Bush.

The focus on Bush 43's legacy signals a big problem for the GOP. Sen. Lindsey Graham (R-S.C.), who declared in a prior debate that he missed the bygone president, pronounced W the winner last night. But no matter how much Jeb Bush defended his brother, or Marco Rubio came to the former president's aid, that Bush's legacy abruptly became a question at all, at this very late date, dealt the establishment a potentially crippling blow.

Yes, the establishment — there's that word again, used advisedly but of necessity. For what was supposed to be more established a fact in the Republican Party but that George W. Bush — at a bare, bare minimum — was the right man in office on Sept. 11? Yet here was Donald Trump, naked in a way few have really seen him before, slamming home the message again and again: W messed up. He hurt the party. And he hurt the country.

"The World Trade Center came down during the reign of George Bush," Trump growled. "He kept us safe? That is not safe." Technically true, but, as is so often the case with Trump, the details came second to theme, and the theme went far beyond 9/11 or the gasps and boos Trump's comments brought. Trump slapped W on Iraq, too. "The war in Iraq was a big, fat mistake. They lied," he said of Dubya's administration. "They said there were weapons of mass destruction. There were none."

Leave aside the particulars. (Saddam's men, ruled by fear and deceit, habitually lied and believed lies about their own WMD and other special weapons.) Trump's eye-popping broadsides against the Bush administration far exceeded some kind of coming-out party as a Democrat. Nor were they animated by a longing to merely belittle Jeb Bush or exact juvenile revenge. Rather, they were illustrative of the sweeping but specific theme of Trump's night and his campaign, revealed with typical deadpan cockiness in his closing remarks.

"Politicians are all talk, no action."

But wait, you say. George W. Bush took lots of action!

"You've seen where they've taken you to," Trump says. "We are [at a debt of] 19 trillion dollars right now […]. We need a very big change." Because, of course, "we don't win anymore."

Vacuous, you say. Pablum.

But consider the logic within. In a culture where "politics" has become an echo chamber — a vain hall of mirrors installed by the worship of rhetoric and self-regard — true politics, the art and science of victory, is dead. The kinds of action that arise from a corrupt political culture, from the corrupted idea that politics is a game of semiotics first, are, therefore, also corrupted: fake actions, actions without integrity, actions born to lose.

Trump is saying that, under George W. Bush, the Republican Party allowed its understanding of politics to be corrupted. For whatever reason, under Bush, the GOP became a party that let self-aware rhetorical posturing dictate the way policy was formulated. The result was failure across the board. Worst of all was the ensuing failure of memory as Republicans forgot the winning arts and sciences. In so doing, they enabled America to lose its way in the hall of mirrors — and lose its greatness.

This is a dagger to the heart of the Bush legacy.

But Trump is not just running against Bushism. He's running against what it's a symptom of — the certain kind of insider sophistry that he says defines the political class. That's why he was onstage at all last night. That's why he's in first place now. And that's why he's more at home in the GOP than so many want to admit.

To understand how that could possibly be, understand what he's not arguing.

The typical critique of politics today is that the ruling class has been corrupted by privilege. There's too much money in politics; there's too much of a cult of access; the tropes go on and on. Trump's not saying that. Instead, he's saying, the ruling class has been corrupted by foolishness. The problem isn't that "the politicians" have vanished behind the velvet rope. It's that they've vanished up their own rear ends. Obsessed with themselves, they have forgotten who they are. They have lost their way — and ours.

Hard as it is to stomach or say, that is a kind of wisdom so deep, so populist, and so potent that many conservatives can't help but flutter toward it. Then again, neither can many moderate or liberal Republicans, which is why Trump performs well across all groups.

To be sure, in some ways Trump is a dreadful messenger for this dreadful message. Then again, watching him work up there like a Soviet wrestler, it's clear this man is not riding a fad or indulging a fantasy. An immense physical and mental strain is involved in hitting his fellow candidates — hungry, disciplined men — on issue after issue. He is delivering an intense message that no one else has proven capable of delivering with the requisite intensity: a shocking insight, when you pause to think about it, but for the fact that in this election year, nothing can shock anymore.