Republican presidential candidates Donald Trump, left, and Sen. Ted Cruz interact at the conclusion of the CNN Republican presidential debate at The Venetian Las Vegas on December 15, 2015.
Justin Sullivan/Getty/FILE
Republican presidential candidates Donald Trump, left, and Sen. Ted Cruz interact at the conclusion of the CNN Republican presidential debate at The Venetian Las Vegas on December 15, 2015.
Now playing
01:23
The Trump vs. Cruz battle for Iowa escalates
Green Party presidential nominee Jill Stein waits to be introduced prior to a press conference at the National Press Club August 23, 2016 in Washington, DC.
Win McNamee/Getty Images
Green Party presidential nominee Jill Stein waits to be introduced prior to a press conference at the National Press Club August 23, 2016 in Washington, DC.
Now playing
01:44
Jill Stein raises millions for recount
Former Democratic US Presidential candidate Hillary Clinton speaks to staff and supporters at the New Yorker hotel after her defeat in the presidential election November 9, 2016 in New York. / AFP / Brendan Smialowski        (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
BRENDAN SMIALOWSKI/AFP/Getty Images
Former Democratic US Presidential candidate Hillary Clinton speaks to staff and supporters at the New Yorker hotel after her defeat in the presidential election November 9, 2016 in New York. / AFP / Brendan Smialowski (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
Now playing
02:14
Scientists urge Clinton to call for recount
LYNDEN, WA - MAY 07: Republican presidential candidate Donald Trump gives a speech during a rally at the The Northwest Washington Fair and Event Center on May 7, 2016 in Lynden, Washington. Trump became the Republican presumptive nominee following his landslide win in Indiana on Tuesday. (Photo by Matt Mills McKnight/Getty Images)
Matt Mills McKnight/Getty Images North America/Getty Images
LYNDEN, WA - MAY 07: Republican presidential candidate Donald Trump gives a speech during a rally at the The Northwest Washington Fair and Event Center on May 7, 2016 in Lynden, Washington. Trump became the Republican presumptive nominee following his landslide win in Indiana on Tuesday. (Photo by Matt Mills McKnight/Getty Images)
Now playing
03:25
Donald Trump's wild ride
Now playing
01:46
Trump's challenges in the Middle East
donald trump undocumented immigrants crime fact check origwx ty_00013807.jpg
donald trump undocumented immigrants crime fact check origwx ty_00013807.jpg
Now playing
02:47
Fact checking Trump on crimes by immigrants
Mark Makela/Getty Images/Lintao Zhang/Getty Images
Now playing
01:26
Trump vs. the tape on Obama and the protester
Now playing
01:28
Trump compares Clinton email probe to Watergate
Members of the Secret Service rush Republican presidential candidate Donald Trump off the stage at a campaign rally in Reno, Nev., on Saturday, Nov. 5, 2016. (AP Photo/John Locher)
John Locher/AP
Members of the Secret Service rush Republican presidential candidate Donald Trump off the stage at a campaign rally in Reno, Nev., on Saturday, Nov. 5, 2016. (AP Photo/John Locher)
Now playing
01:20
Donald Trump rushed off stage by Secret Service
AFP/Getty Images
Now playing
02:16
Trump reads letter from Patriot's coach at rally
US Republican presidential nominee Donald Trump speaks during rally at the Atkinson Country Club in Atkinson, New Hampshire on November 4, 2016.
Mandel Ngan/AFP/Getty Images
US Republican presidential nominee Donald Trump speaks during rally at the Atkinson Country Club in Atkinson, New Hampshire on November 4, 2016.
Now playing
01:56
Trump on US officials: 'What a group of losers'
donald trump nice and cool pensacola fl bts_00001523.jpg
donald trump nice and cool pensacola fl bts_00001523.jpg
Now playing
00:49
Trump's mantra in campaign's final week: Stay on point
donald trump nice to hillary clinton and democrats orig cm_00000000.jpg
donald trump nice to hillary clinton and democrats orig cm_00000000.jpg
Now playing
01:52
Audio of Trump praising the Clintons and Democrats
cuomo lewandowski hillary clinton email exchange newday_00002327.jpg
cuomo lewandowski hillary clinton email exchange newday_00002327.jpg
Now playing
01:28
Cuomo grills Lewandowski on Clinton email 'hypocrisy'
Now playing
00:10
This video is no longer available
Now playing
01:49
Meet the other Hillary Clinton and Donald Trump
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.”