Dried blood on the window of Paris’s Carillon cafe. Photo: Jerome Delay/AP

In the aftermath of mass murder in Paris, Establishment Republicans posited hopefully that now, finally, their voters would get serious and support a presidential candidate who had professional experience in the field of politics. A few days after the attacks, Politico reported the firm convictions of party stalwarts, who confidently asserted, “The reemergence of foreign policy atop the Republican agenda will force voters to reevaluate the outsider candidates, particularly as both [Donald] Trump and [Ben] Carson display a lack of knowledge about national security and the terrorist threat.”

But that, it turned out, was wishful thinking. Far from sobering up the Republican electorate, the attacks served instead to ­intensify its state of frothing rage. A poll showed that the candidate Republicans trusted most to handle terrorism, and the candidate who found his overall lead in the polls rising again after an autumn sag, was none other than Donald J. Trump. And, indeed, this development may have been predictable. From the standpoint of a Trump skeptic, it makes no sense to entrust the task of addressing large policy problems to a buffoonish demagogue; post-Paris, it makes even less sense to entrust one with solving problems now revealed to be even larger.

From the standpoint of a Trump fan, however, things look quite different: The country desperately needs a strong leader who can assure it of victory and who will look after its people without being held back by diplomatic niceties or moral decency, goes the thinking. Gazing upon the bloody streets of Paris and the hordes of suspicious-looking foreigners desperate to take refuge in the United States, his supporters see the allure of a Trump ­presidency now more than ever.

The enveloping climate of fear extends far beyond Trumpian knuckle-draggers, however. A CNN reporter at a press conference asked President Obama, “Why can’t we take out these bastards?” Polls conducted days after the Parisian atrocities showed substantial majorities in favor of sending ground troops to fight ISIS and against allowing more ISIS-fleeing refugees into the U.S. America is relying on its lizard brain.

The atmosphere after Paris provided the nearest approximation to the mix of dread, rage, and suspicion that pervaded American politics after 9/11. And once again, a Bush responded by instinctively proposing to send ground troops to occupy a Middle Eastern country. This time it was Jeb, characteristically blind to the prospect that American ground troops would allow ISIS to refashion itself as the authentic local resistance to a Western invasion. At a recent campaign event, one voter asked if the ­Middle East was safer with or without Saddam Hussein ruling Iraq. Bush replied, “We can have a history lesson or we can talk about the fact that I’m running for president.” (This is the closest Bush has come to openly acknowledging that his election would require voters to forget everything that happened in the recent past.)

France, the target of the attacks, responded somewhat like our country did after 9/11: striking back at the enemy militarily. (President François Hollande vowed to wage a “pitiless” war.) But the United States has changed since the last time it had a Bush in office—in large part because it had a Bush in office. The current president, elected in no small part owing to widespread disgust with the Iraq War, has no ready-made policy response to sate the public’s anger. The Obama administration had an anti-ISIS strategy in place before Paris: air strikes, limited use of special forces, aid to proxies on the ground, and the use of intelligence and law enforcement to ward off threats. The attacks in Paris were a horror but not a revelation; the administration already knew ISIS wanted to murder enemy civilians, including Westerners, indiscriminately.

Because Obama — unlike Bush in 2001 and Hollande today — had no change of action in response, the nationalistic impulses unleashed by the attacks have flowed into different channels from the ones 14 years ago. The American backlash has taken on a wildly xenophobic character this time around. Despite the fact that the Paris attacks were not carried out by Syrian refugees, that France itself vowed to continue its refugee program following the attacks, and that the United States was taking a fraction of the exiles that its (much smaller) European allies were, American fears settled on the possibility that refugees might replicate the horrors of Paris on American soil.

In theory, ISIS could certainly plant terrorists among refugees. In practice, refugees undergo a screening process that lasts an average of two years, and officials dismiss the risk as minimal. Anne C. Richard, the assistant secretary of State for population, refugees, and migration, told a House committee, “The odds of a refugee becoming a terrorist are very, very small.” No risk can be eliminated, of course. Alcohol, pizza, automobiles, not to mention millions and millions of guns, all pose risks. One might even wonder why the risk that deranged men loyal to ISIS might gun down civilians should terrify a country already inured to these sorts of slaughters carried out by men afflicted by different derangements. A rational or even semi-rational approach to the situation might balance the danger of terrorists’ hiding among the refugee population against the humanitarian benefits of saving innocent people from the horrors of civil war and ISIS’s medieval barbarism.

No such reasoning has cooled the feverish response, however. Obviously, every country gives the interests of its own ­people more weight than the interests of others. The essence of nationalism is to disregard the interests of other countries completely. “We are a compassionate nation,” announced House Speaker Paul Ryan, employing the usual lead-in for endorsing uncompassionate policies, “but we also must remember that our priority is to protect the American people.” And by “priority,” Ryan made clear, he really meant “only consideration.” Specifically he said, “We should not bring Syrian refugees into this country unless we can be 100 percent confident that they are not here to do us harm.” A 100 percent certainty is an extremely high threshold. This is the immigration-policy analogue of Dick Cheney’s One Percent Doctrine, which held, in the wake of 9/11, that even a one percent chance of terrorists’ obtaining weapons of mass destruction must be treated as a certainty.

Republican leaders have struggled, with mixed results, to suppress the xenophobic undertones on the right for fear that their party will alienate the growing share of Latino voters. The Muslim voting bloc — being smaller, harder to measure, and not as politically useful — has no such leverage. Thus this new iteration of the immigration debate has subjected its targets to unrestrained savagery. Rand Paul vowed to “end housing assistance to refugees.” Ted Cruz and Jeb Bush both proposed to let in only Christian refugees, untroubled by the legal and practical obstacles to attaching a formal religious test to government policy.

The terms conservatives used to explain their reasoning served only to confirm their cruelty. “If there’s a rabid dog running around in your neighborhood, you’re probably not going to assume something good about that dog, and you’re probably going to put your children out of the way,” said Ben Carson about Syrian refugees. “It doesn’t mean that you hate all dogs, by any stretch of the imagination, but you’re putting your intellect into motion.” Marco Rubio, meanwhile, objected to Hillary Clinton’s denial that the United States is at war with Islam like so: “That would be like saying we weren’t at war with the Nazis, because we were afraid to offend some Germans who may have been members of the Nazi Party but weren’t violent themselves.” In Carson’s analogy, terrorists are like rabid dogs, and Muslims like all dogs. In Rubio’s analogy, terrorists are like violent Nazis, and regular Muslims are like nonviolent Nazis. Trump insisted, falsely, that he had seen thousands of American Muslims cheering the 9/11 attacks. (Confronted with the fact that there’s no evidence of such a thing: “I have the world’s best memory.”) This time around, the right-wing mind has come to fixate on the imagined enemy at home rather than the real one abroad.

It is Trump who has set the pace. His talent for manipulating the darkest emotions of the conservative id, while minimizing specific policy commitments, has been on full display. In every public appearance, he emitted new, authoritarian-sounding warnings. “We’re going to have to do things that we never did before. And some people are going to be upset about it, but I think that now everybody is feeling that security is going to rule,” he vowed. “We’re going to have to look at the mosques. We’re going to have to look very, very carefully.” Every new sound bite set off a profitable fervor of media speculation, forcing other candidates to raise the bidding or be left behind. “It’s not about closing down mosques,” insisted Rubio, placing himself rhetorically to Trump’s right, “it’s about closing down anyplace — whether it’s a café, a diner, an internet site — anyplace where radicals are being inspired.”

The tea-party movement had initially fashioned itself as wildly anti-statist. Now its advocates have veered into wild authoritarianism. None of this requires intellectual justification in lizard-brain America, and Trump, for now, is the Lizard King.

This article appears in the November 30, 2015 issue of New York Magazine.