Trump: Cruz must settle Canadian 'problem' or drop out
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Republican presidential front-runner Donald TrumpDonald John TrumpIG investigating Comey memos over classified information: report Overnight Defense: Congress poised for busy week on nominations, defense bill | Trump to deliver Naval Academy commencement speech | Trump administration appeals decision to block suspected combatant's transfer Top Pruitt aid requested backdate to resignation letter: report MORE is doubling down on his attacks against rival Ted CruzRafael (Ted) Edward CruzCruz's Dem challenger slams Time piece praising Trump Race for Republican Speaker rare chance to unify party for election 32 male senators back Senate women's calls to change harassment rules MORE, saying the Texas senator needs to "settle" his Canadian birth "problem" or drop out of the race.

"It's time for Ted Cruz to either settle his problem with the FACT that he was born in Canada and was a citizen of Canada, or get out of the race," Trump tweeted Monday morning.

Cruz has dismissed Trump's criticism, maintaining he is eligible for the presidency because he is the child of a U.S. citizen.

This past weekend, Trump told a crowd of supporters in the Sioux City, Iowa, that he may file a lawsuit over Cruz's eligibility to serve in the Oval Office.

"Can you imagine if I did it? Should I do it just for fun?” Trump asked. 

During the speech, Trump said Democrats would sue within days if Cruz won the GOP nomination. He also brought up other lawsuits that have already been filed.

Earlier this month, a Texas attorney filed a lawsuit questioning Cruz's eligibility. The case argued that the Supreme Court must decide the issue.

“The U.S. Constitution is not a popularity document for fair weather only,” says the federal lawsuit, filed by Newton Schwartz. “However persuasive one finds each side in this debate, the final decision ultimately rests in the hands of five or more of nine Justices on the Supreme Court as mandated by the Constitution.”

With just about week left before the Iowa caucuses, Trump continues to lead in polls both nationally and in Iowa. In the RealClearPolitics average of polls in Iowa, Trump leads Cruz — his closest competitor — by 5.2 points.