James Carville: Donald Trump doesn't 'know jack s---'

James Carville on Tuesday delivered harsh criticism of Donald Trump's knowledge of key foreign-policy issues.

In an interview with Business Insider, President Bill Clinton's former campaign manager said that while he disagreed with former Republican presidential candidates like Sen. John McCain and former Massachusetts Gov. Mitt Romney on policy, they were far more well-versed in the details of governing than the current GOP nominee.

"We'd say in Louisiana, he don't know jack s---," Carville said of the Republican presidential nominee.

"There's certain elementary knowledge [you need] to be in anything in politics, much less the president of the United States," he added.

Carville criticized both Trump's threat to start a trade war with China and his suggestion that the US could abandon NATO allies if they do not "fulfill their obligations" to meet certain requirements.

"For one minute, digest a 35% tariff - assuming that you'd ever put it on - but imagine you'd even threaten that. What would that do? How would the markets react to the fact that we're entering a trade war?" Carville said.

Carville acknowledged that he found Trump "kind of funny," he brushed off observers who point out that Trump draws larger crowds to his campaign events than Clinton draws to her.

"Somebody said, 'Well, he gets bigger crowds than Hillary.' And my answer is, 'Yeah, more people lineup to see a trainwreck than a traffic light.' So what the hell does that mean?" Carville said.

The Clinton campaign and its allies have frequently attempted to cast doubt on the real-estate magnate's ability to effectively manage US relationships abroad. Earlier this month, the campaign rolled out a letter co-signed by a number of Republican foreign-policy experts denouncing Trump's policies and positive statements about Russia.

Trump has responded in kind, accusing Clinton and the Obama administration of neglecting to quash the unrest in Syria that led to the rise of ISIS.

"Hillary Clinton's reckless policies unleashed ISIS onto the world. She will never have the judgment or the stamina to fix the problems she created," Trump said in a Wednesday speech in Florida.