As Donald Trump has continued upping the fascist ante and dominating in the Republican primary polls, a familiar refrain has sounded from certain left-leaning quarters. Progressive people well-versed in all the darkest chapters of American history point to the many atrocities visited on Muslims and other minorities over the years, and argue that Trump is basically nothing new.

On Facebook, Teju Cole pointed to the grim legacy of Iraq, Afghanistan, Guantanamo, drones, and so forth, and concluded: "Our legitimate dismay at Islamophobic statements must be situated inside this recent history, a history in which a far wider swath of the country than Trump's base is implicated." Dylan Matthews argued that fascism was an unnecessary concept for understanding Trump.

On one level, these critics have a good point. It's important to situate Trump in an American history with much truly abhorrent character. Trump did not come from nowhere, and he is not without precedent. But shrugging off his rise by saying so smacks of reflex and risks missing the forest for the trees. Much American history is very dark, but things can always get worse.

The question is one of perspective. Yes, the wars in Iraq and Afghanistan were disastrous, bloody failures. The drone war is a hellish nightmare. The Bush torture program was a gigantic war crime, and it is a blight on President Obama's legacy that he did not prosecute anyone responsible. There are more atrocities basically wherever one chooses to look in history. Witness the American-backed coups, dictatorships, and civil wars across the world, or virtually 100 percent of CIA actions, or Jim Crow, or the entire antebellum South.

American history is plenty dark.

It's also true to argue, as Brian Beutler does, that Trump is not really that far outside the Republican mainstream. Republican politics have been increasingly openly xenophobic and prejudiced for decades now. The big difference is Trump just doesn't bother to hide it. Even his idea for totally banning all Muslim entry into the United States isn't very far afield from individual states attempting to prevent the settlement of Syrian refugees.

Yet this does not mean that Trump is a normal product of American politics. In 2012, Norman Ornstein and Thomas Mann famously argued, "The GOP has become an insurgent outlier in American politics. It is ideologically extreme; scornful of compromise; unmoved by conventional understanding of facts, evidence and science; and dismissive of the legitimacy of its political opposition." That was before that year's election — but according to political science measures, Republicans in Congress have become significantly more conservative during the following two cycles.

I submit that Trump represents a tipping point in the continual radicalization of the Republican Party — only this time on race and prejudice. As the infamous Lee Atwater quote demonstrates, conservatives have feared to traffic in overt prejudice since the civil rights movement. But Trump is running the most nakedly bigoted campaign since George Wallace in 1968 at least. A critical mass of Republican voters — a recent poll found that nearly two-thirds of likely GOP primary voters support Trump's plan to ban Muslim entry — have completely abandoned themselves to prejudice. No amount of media backlash or tut-tutting will convince them otherwise — indeed, it will probably backfire. And unlike Joe McCarthy or Father Coughlin, there is no other institution with the credibility to take down Trump.

If Trump wins the Republican nomination, he will surely be defeated handily by any Democrat, right? No. It would not be a sure thing at all. In a two-party system, each side always has a chance.

Would a President Trump actually attempt to deport all 11 million unauthorized immigrants? Would he imprison or deport all 2.75 million American Muslims (who are, by the way, generally successful and quite well-integrated socially)? Would he nuke Syria, or Iran? Would he attempt a coup d'etat to install himself as dictator?

Probably not, but at this point, no responsible person can dismiss such possibilities out of hand. Moreover, as Ned Resnikoff argues, the forces unleashed by Trump will persist long after he is gone. Already, the Republican Party is remaking itself to take advantage of Trumpism's fervent political energy — and now that he has plowed the ground, a less buffoonish successor could easily take up his mantle without seeming nearly so extreme.

Consider FDR, a racist whose signature New Deal was premised on the exclusion of minorities. Yet he and his Democratic successors made the initial political moves towards civil rights policy. He ordered the internment of innocent Japanese-American citizens — yet he did not exile or massacre them.

My point is that while American actions have often been exceedingly grim, political institutions and norms have kept what awfulness there was within certain boundaries. As George Orwell wrote, "An illusion can become a half-truth, a mask can alter the expression of a face." Trump may well be something unprecedentedly terrible.