GOP presidential front-runner Donald Trump has not let up on his argument that Ted Cruz's Canadian birth would lead to trouble if the Texas senator were elected to the White House.

The real estate tycoon predicted on Jan. 10 that Democrats would file lawsuits challenging Cruz's eligibility, insisting that his rival had a legal "cloud" hanging over his head and that the term "natural born citizen" -- one of the requirements the U.S. Constitution spells out to serve in the nation's highest office -- was not yet clearly defined, NBC News noted.

"Does anyone know more about litigation than Trump?" he asked as he warned of potential Democratic moves to reverse a Cruz victory. "I know a lot; I'm like a Ph.D. in litigation."

"From Ted's standpoint, and from the party's standpoint, he has to solve this problem," the front-runner insisted, according to Real Clear Politics. "Because the Democrats will sue him if he is the nominee. If Ted is the nominee, he will be sued by the Democrats. And according to one of the great lawyers of the country... the whole thing, this matter has not been determined."

Cruz, who was born in Calgary, Canada, to an American mother and a Cuban father, renounced his Canadian citizenship in 2013, according to the Canadian Broadcasting Corporation. But Trump questioned on Jan. 10 why the senator had not taken that step earlier.

"He said he didn't know about it, OK. Does he get a pass for that?" the former "Apprentice" star said. "It's sort of like, Hillary's got a problem too. She doesn't know whether or not she's gonna be indicted. She's got the cloud hanging over her head, but Ted Cruz has a real cloud hanging over his head."

Trump was adamant, meanwhile, that his frequent remarks about Cruz's eligibility were not an attempt to disqualify his rival from the presidential race over a technicality.

"I would rather win it straight up," he told supporters on Jan. 10. "If I'm a fighter, I wanna knock the guy out, I don't wanna default because he couldn't like meet the weight class or something."

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