"Look, we're led by a man that either is not tough, not smart or he's got something else in mind," the presumptive Republican nominee told Fox & Friends Monday morning.
Earlier in the interview, when asked why he called for Obama's resignation, Trump said, "He doesn't get it or he gets it better than anybody understands. It's one or the other."
Also during that interview, Trump repeated a four-word phrase that has come to define his conspiratorial campaign almost as much as his official slogan, "Make America Great Again."
"There's something going on," Trump said. "It's inconceivable. There's something going on."
That phrase, according to political scientists who study conspiracy theories, is characteristic of politicians who seek to exploit the psychology of suspicion and cynicism to win votes.
The idea that people in positions of power or influence are conspiring to conceal sinister truths from the public can be inherently appealing, because it helps make sense of tragedy and satisfies the human need for certainty and order. Yet politicians hoping to take advantage of these tendencies must rely on vague and suggestive statements, since any specific accusation could be easily disproved.
"He's leaving it to the audience to piece together what he's saying," said Joseph Uscinski, a political scientist at the University of Miami, in a recent interview.
Trump's rhetoric has fit this pattern, particularly his repetition of the phrase, "There's something going on." He said the same thing with reference to the deadly attack in San Bernardino last year at a debate in January.
"There’s something going on there," Trump told MSNBC's Morning Joe in November when asked whether Islam is a violent religion. "There’s something definitely going on."
Uscinski noted that Trump has used the tactic throughout his campaign to gain support by appealing to voters' fears and cynicism.
"The one thing that’s remained absolutely consistent is his penchant for conspiracy theorizing," Uscinski said.
Polling during the primary showed that Trump was especially popular with Republicans who endorsed conspiracy theories.
His supporters were more likely than supporters of Sen. Ted Cruz (Tex.) and Ohio Gov. John Kasich to agree with the statement, "President Obama is hiding important information about his background and early life," according to the data from Fairleigh Dickinson University in New Jersey.
The poll found also found that Trump's supporters were more likely to believe that vaccines cause autism, that global warming is a hoax and that Democratic presidential front-runner Hillary Clinton intentionally did not act to prevent the deaths of Americans in Benghazi, Libya, in 2012.
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