Donald Trump takes aim at Ted Cruz

Windham, New Hampshire (CNN)Donald Trump was in New Hampshire on Monday but his audience was really in Iowa.

With three weeks until the Iowa caucuses, Trump is trying to break Ted Cruz's tenuous grip on first place in the state. At a morning rally here, Trump again raised questions about whether the Texas senator is eligible to become president because he was born in Canada.
"He's got a problem," Trump said. "Whether you like it or not, Ted has to figure it out."
He went on: "You can't have a nominee who's going to be subject to being thrown out as the nominee. You just can't do it. So you gotta make that decision, folks."
    Trump is dominating here in New Hampshire, where a new poll out Monday from Monmouth University found him leading the race at 32%, nearly 20 percentage points ahead of his closest rival. But Iowa has been tougher for him as recent polls have found Cruz ahead. That could be changing, though, as a poll out Monday from Quinnipiac University had Trump edging Cruz 31%-29%.
    Wins in Iowa and New Hampshire would provide Trump plenty of momentum heading into other GOP primaries.
    Trump is zeroing in on Cruz's Canadian birth as he tries to remove the senator as a threat to his candidacy. The Constitution requires a candidate be a "natural born citizen" to be eligible to be President, a qualification most legal scholars agree includes individuals born abroad to an American parent -- like Cruz.
    The issue has never been tested in federal court, a fact Trump reminded his audience of on Monday: "It's not a settled matter."
    Trump first flagged the issue of Cruz's birthplace in an interview with the Washington Post last week, in which Trump called the issue "very precarious."
    Trump has since repeatedly brought up the issue unprompted on the stump and said this weekend in a pair of Sunday television interviews that "I really don't know" if Cruz qualifies as a natural born citizen.
    Trump on Monday pointed to Harvard scholar Laurence Tribe who has also raised questions about Cruz's eligibility. Trump also cited Democratic Rep. Alan Grayson, a Florida Senate candidate who has threatened to hit Cruz with a lawsuit challenging his eligibility to serve as president.
    Trump's questioning of Cruz's eligibility to serve as President dogged Cruz all week as he swung through Iowa on a 6-day, 28-stop bus tour, with the Texas senator forcefully insisting that he meets the qualifications to serve as president, given his mother's American citizenship at the time of his birth.
    "The Internet has all sorts of fevered swamp theories, but the facts are simple," Cruz told CNN's Jake Tapper in an interview that aired Sunday on "State of the Union." "My mom was born in Wilmington, Delaware. She was an American citizen by birth. She's been an American citizen all 81 years of her life. She's never been a citizen of any other place."