U.S. Republican presidential candidate Donald Trump speaks during a campaign event at Iowa Central Community College in Ft. Dodge, Iowa, November 12, 2015. REUTERS/Scott Morgan

One fascinating recent discovery in political science research is that partisans increasingly believe in conspiracy theories when their party is out of office. Seven years into the Obama administration, some researchers say that pattern can help explain why Donald Trump is so popular.

In the Republican debate Thursday night, Trump invoked a new conspiracy theory using just eight syllables, the kind of phrasing that can flame anxieties without actually saying anything specific.

"There's something going on, and it's bad," Trump said.

Trump has used the same phrase repeatedly during the campaign. "There's something going on with him that we don't know about," he recently said of Obama. "There's something going on in the mosques," he told an audience in Myrtle Beach, S.C. in November. "There's definitely something going on," he said again a few days later, when asked about Islam.

Trump never quite says exactly what he thinks might be going on, though. He doesn't need to. The key is to raise suspicion.

"Trump is using the fact that, psychologically, humans are, in the face of these kinds of harrowing events, looking for explanations that satisfy our deep needs for order, certainty and control of the world around us," Colorado State University's Kyle Saunders, who has studied conspiracy theories, wrote in an email. "Trump is, for those who buy into his explanation, reducing fear and anxiety about the uncertainty of the world--and, to me, this explains much of Trump's recent ascent."

This tactic was on display in textbook form Thursday night.  Trump's comments, though they might have been difficult to follow, are worth analyzing in detail.

Trump was talking about the carnage in San Bernardino, Calif. last month, in which 14 people died. So did two heavily armed attackers: Syed Rizwan Farook and Tashfeen Malik, a husband and wife.

The attacks, Trump seemed to suggest, could have been prevented. He said that the couple's friends and family were aware of the arsenal they were acquiring. "Many people knew about what was going on," he said. "Why didn’t they call the police?"

"He evokes this idea that there is a large group of people who all knew what was going on with the San Bernardino shooting and decided to keep it secret or potentially aid them in what they were going to do," said Joseph Uscinski, a political scientist at the University of Miami and an expert on conspiracy theories.

"He's leaving it to the audience to piece together what he's saying," Uscinski added. "The implication is fairly clear."

Trump also implied the full story about what happened in San Bernardino isn't yet known. "I want to find out," he said. "We'll get to the bottom of it."

A comment like that might have made sense shortly after the attack, Uscinski said, but not more than a month later, after law enforcement has had time to interview the perpetrators' associates, search their apartment and begin reconstructing damaged hard drives.

"If we need to get to the bottom of a shooting that’s been thoroughly investigated, then it almost implicates the authorities who have been investigating it," Uscinski explained.

In the San Bernardino case, that's the Federal Bureau of Investigation.

"Perhaps it is that the current administration isn’t motivated to uncover the secret network of terrorists that are still at large in San Bernardino," Uscinksi said, offering a possible interpretation of Trump's remarks.

Some of these questions might seem quite reasonable to ask, but Trump's tone suggests something is amiss, someone can't be trusted.

Uscinski noted that the real-estate magnate's logic is similar that of the theorists who, following the tragedy of September 11, 2001, suggested that the Bush administration had abetted the attacks. Evidence that some people were aware of suspicious activity but did nothing leads, in both cases, to the conclusion that those other people were part of the plot. Since official explanations do not accuse these other people, the logic goes, those official accounts must be a cover-up.

Like those earlier conspiracy theorists, Trump never quite says out loud what he's suggesting, which would expose how implausible his thinking is. "The more explicit you get, the more indefensible it becomes," Uscinski said.

Here are Trump's words, in full:

We have a serious problem with, as you know, with radical Islam. We have a tremendous problem. It's not only a problem here. It's a problem all over the world.

I want to find out why those two young people -- those two horrible young people in California when they shot the 14 people, killed them -- people they knew, people that held the wedding reception for them. I want to find out -- many people saw pipe bombs and all sorts of things all over their apartment. Why weren't they vigilant? Why didn't they call? Why didn't they call the police? ...

We have to find out -- many people knew about what was going on. Why didn't they turn those two people in so that you wouldn't have had all the death?

There's something going on and it's bad. And I'm saying we have to get to the bottom of it. That's all I'm saying.

Trump's latest theory is that there is something the public doesn't know about the attacks in San Bernardino. And the cryptic nature of his questions suggests maybe somebody is hiding something. This may well appeal to supporters. As Wonkblog recently reported, conservatives who are more knowledgeable about politics in general are also more likely to subscribe to certain conspiracy theories.

[Read more: Why smart people believe all the crazy things Trump says]

But liberals can also exhibit this type of thinking. A group of political scientists asked people to take a short quiz with several general questions about current U.S. politics. Then they asked them to say whether they believed a range of conspiracy theories. The chart below shows which theories had the widest support in the study.


They found that the conservative respondents who did better on the quiz were also more likely to say they believed in the conspiracy theories that named liberals as villains.

That could be because people who are more paying attention politically are also more likely to feel more strongly about political issues, so the temptation for them to believe in falsehoods that impugn their political opponents is greater. And this group is also better able to see how an obscure conspiracy theory might support or undermine their political convictions.