Conservative commentator Ann Coulter, who has been supporting Donald TrumpDonald John TrumpSchiff: Surveillance warrant docs show that Nunes memo 'misrepresented and distorted these applications' Chicago detention facility under investigation following allegations of abuse of migrant children Ex-Trump aide: Surveillance warrants are 'complete ignorance' and 'insanity' MORE for president, took to Twitter on Wednesday to declare that Sen. Ted CruzRafael (Ted) Edward CruzCruz: 'I'm glad' Disney fired James Gunn over 'horrible' tweets Washington needs to end hidden inflation tax on our capital gains GOP tax writer introduces bill to reduce capital gains taxes MORE (R-Texas) is not a natural born U.S. citizen.

Coulter joins Trump in questioning whether Cruz can legally be president.

“Republicans are going to have to ask themselves the question: ‘Do we want a candidate who could be tied up in court for two years?’ That’d be a big problem,” Trump told The Washington Post on Tuesday.

The U.S. Constitution states that to be eligible for the White House, one must be a “natural born citizen.” That’s long been interpreted to include anyone born to a U.S. citizen, even outside the country.

Cruz was born in Canada to an American mother and Cuban father. For years he held dual U.S.-Canada citizenship. The Texas Republican renounced his Canadian citizenship after he became a U.S. senator.

Cruz has laughed off the suggestion he’s not eligible for the White House, taking to Twitter on Tuesday to post a link from the television show “Happy Days” that shows the character Fonzie on water skis jumping over a shark.

Cruz and Trump are battling atop the polls in Iowa with less than a month to go before the caucuses there.