Scott Walker Doesn't Rule Out Building a Fence Along US-Canada Border

— -- When it comes to securing the nation's borders, Wisconsin Gov. Scott Walker says he has heard "legitimate concerns" from voters about the need to strengthen security along the U.S. border with Canada, not just Mexico.

Asked by NBC about the notion of building a fence along the Canadian border, the Republican presidential candidate said it's an issue "for us to look at."

"Some people have asked us about that in New Hampshire," Walker told NBC News' Chuck Todd in a "Meet the Press" interview that aired Sunday.

"They have raised some very legitimate concerns, including some law enforcement folks that brought that up to me at one of our town hall meetings about a week and a half ago. So that's a legitimate issue for us to look at."

Walker, who has made border security a central focus of his broader national security platform, told Todd "we need to secure the borders in general," citing the southern border with Mexico as having the "most rampant spots" for illegal border crossings.

"If we're spending millions of dollars on TSA at our airports, if we're spending all sorts of money on port security, it only makes sense to me that, if part of what we're doing is protect ourselves, and set aside immigration for a minute, but protect ourselves from risk out there, I think we should make sure we have a secure border," he said.

Since first making the comment to NBC, Walker has taken to Twitter to double down on his stance that a northern border fence is an idea worth considering. The campaign declined to comment today, instead directing ABC News to his tweet:

Vermont Democratic Sen. Patrick Leahy, whose state borders Canada, issued a statement today calling Walker's comment "one of the craziest" ideas he has heard this election.

“As someone who was born and raised not too far from the Canadian Border, I could not believe Governor Walker’s statement. Election season always brings out crazy ideas, but this is one of the craziest,” Leahy said in a paper statement. "Governor Walker simply must be unaware of the economic prosperity that commerce across the northern border brings to the United States. Those of us who represent states that share a border with Canada know better."

Walker's comments to Todd mark the first time that the presidential candidate has expressed concern about the security of the nation's northern border, though he has previously warned about terrorists penetrating the border with Mexico. In a speech at the Citadel military college in South Carolina last week, Walker warned that terrorists could be penetrating the U.S.-Mexico border, using the same routes as immigrants crossing the border illegally.

“You see, Islamic extremists and other terrorists are most likely using the same trails into our homeland as the drug cartels, the weapons smugglers and the human traffickers," Walker said Friday in what was the first major foreign policy speech of his presidential campaign.

Border security has become a driving issue in the Republican presidential contest since front-runner Donald Trump surged to the top of the polls with an immigration platform that calls for building a wall along the U.S.-Mexico border, deporting all immigrants in the country illegally and revoking birthright citizenship for children of immigrant parents who entered the United States illegally.

Walker, who was the clear front-runner in Iowa polls for much of the year, has recently fallen into the single-digits in that state as Trump has surged to the top of the field.