Yesterday's paranoid types feared elite groups such as the Illuminati and the Masons. Today's bogeymen include the members of the Rockefeller-founded Trilateral Commission and the politicians and financiers who attend the monied confab at Bohemian Grove and are suspected of mapping out the "new world order."

Or consider immigration. In the 1850s, the nativist American Party (also known as the Know-Nothings) formed over fear of the new immigrants -- Irish and German -- coming to the United States, allegedly stealing jobs. Today, there's Arizona SB 1070, nicknamed the "show me your papers" law. Though parts of the law were shot down by the U.S. Supreme Court, other states have used it as a model, and immigrant suspicion is routinely in play -- especially along the southern border. This despite studies that have shown that immigrants don't take jobs away from U.S. citizens.

Even suspicion of an internal coup remains. In the 1950s, we had the Red Scare; today there are people claiming the coming of Sharia law; rumors about Agenda 21, a United Nations development initiative that has inspired fears of world government; and the always reliable anti-Semitism, whether it concerns the "Zionist media," blame for 9/11 or a belief that Israel is pulling the strings of the U.S. government.

For Hofstadter, the "Paranoid Style" was an extension of two decades of work that promoted reason over emotion and critiqued America's fondness for an idealized, agrarian past, says his biographer, Elizabethtown College history professor David S. Brown. By the time he wrote the essay, the two-time Pulitzer Prize winner was convinced that all those pesky extremists were a thing of the past. But he was well aware that consensus was fragile.

As Derek Arnold, a Villanova communications professor, observes: "You can almost see him as pretty prescient."

'Leaving rationality behind'

It's certainly easy to fall under the spell of paranoia. Since the dawn of mankind, we have been clannish and tribal animals, wary of others, fused by emotional connections. In the modern world we create tribes beyond blood -- like sports fans or, well, political parties.

The danger is that many people don't develop the rationality to tamp down the emotion, says Dr. David Reiss, a San Diego-based psychiatrist who studies personality dynamics.

"It's not so much that they're paranoid in a clinical sense, but if they feel their needs are going to be met -- or they're connecting with someone powerful -- they're basically leaving rationality behind," he says.

Then there's another deeply human element: the attraction of the story.

"If it's something that's interesting and grabs your attention, regardless of your background, it's appealing," says Villanova's Arnold. He mentions the theories about the Mayan calendar predicting catastrophe. "Look at the end-of-the-world stories we've been getting this year."

Though much of the focus these days is on right-wing paranoia, both sides, as they get more extreme, look at their opposition as the enemy and hold on more tightly to their own beliefs, says Jonathan Haidt, a professor of moral psychology at NYU and the author of the recently published "The Righteous Mind: Why Good People Are Divided by Politics and Religion."

"Extremism on either side leads to very predictable patterns of thinking and usage of fact," he says. "Morality binds and blinds. As long as you're on a team, you'll have your own set of values and facts."

Extremists on both sides often take leaps beyond the logical. They indulge in hyperbole: for the left, the right is engaged in a "war on women"; the right has talked about the left waging a "war on religion." (After the massacre in Aurora, Colo., Texas Republican Rep. Louie Gohmert attributed the tragedy to "ongoing attacks on Judeo-Christian beliefs.")

Why don't believers follow logic? Again, the mind's fascination with patterns and groupings is to blame, says Assumption's Vaughn: We use shortcuts to make decisions, often dictated by our biases.

Add to that our tribal instincts, and shades of gray are reduced to a black-and-white world.

"It's something you can understand," he says. Those who don't see things the same way, he continues, are the deluded ones.

Cashing in

Minnesota Rep. Keith Ellison, a Democrat and one of only two Muslims in Congress, has seen plenty of fear-mongering, whether it's accusations that up to 81 members of the Congressional Progressive Caucus are communists or that Huma Abedin, a Hillary Clinton aide, has ties to the Muslim Brotherhood.

He believes the accusations are tied to both demagoguery and paranoia -- "there are people who have an appetite for conspiracy" -- but undergirding it is something even more elemental in politics: money.

"It is lucrative," he says. "As long as there is a financial payoff, and it also happens to feed their paranoia and thirst for conspiracy, it's going to keep going -- until the American people just totally reject it."

Avlon, the "Wingnuts" author, agrees.

"People who listen to partisan media don't appreciate that what they have taken to be a tribe of true believers is nothing more than a business plan," he says.

Indeed, there is good money in playing to your audience. the more the audience buys into it, the harder it is to dislodge their beliefs.

Writer Charles P. Pierce laid out the rules in his indispensable book "Idiot America": "1. Any theory is valid if it sells books, soaks up ratings or otherwise moves units. 2. Anything can be true if someone says it loudly enough. 3. Fact is that which enough people believe (and) Truth is determined by how fervently you believe it."