Story highlights "If he gets the nomination, they're going to sue his ass up," Trump told a crowd of supporters

Trump has repeatedly raised the subject of Cruz's birthplace

Milford, New Hampshire (CNN) Donald Trump's harping on Ted Cruz's Canadian birthplace wasn't enough to help him win the Iowa caucuses.

But he's not ditching that line of attack.

"If he gets the nomination, they're going to sue his ass up," Trump told a crowd of supporters here on Tuesday.

Trump has repeatedly raised the subject of Cruz's birthplace, suggesting that the Texas senator, who was born in Calgary, Alberta, to an American mother, may not be constitutionally eligible to serve as president of the United States. The Constitution requires the president to be a natural-born citizen, which Trump and some legal experts contend requires the person be born on American soil.

The matter has never been settled in federal court, but most legal experts side with Cruz in asserting that his birth to an American mother makes him a natural-born citizen.

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