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DES MOINES, IA - AUGUST 17:  Republican presidential candidate and Wisconsin Gov. Scott Walker speaks to fairgoers during the Iowa State Fair on August 17, 2015 in Des Moines, Iowa.  Presidential candidates are addressing attendees at the Iowa State Fair on the Des Moines Register Presidential Soapbox stage and touring the fairgrounds. The State Fair runs through August 23.  (Photo by Justin Sullivan/Getty Images)
DES MOINES, IA - AUGUST 17:  Republican presidential candidate and Wisconsin Gov. Scott Walker speaks to fairgoers during the Iowa State Fair on August 17, 2015 in Des Moines, Iowa.  Presidential candidates are addressing attendees at the Iowa State Fair on the Des Moines Register Presidential Soapbox stage and touring the fairgrounds. The State Fair runs through August 23.  (Photo by Justin Sullivan/Getty Images)

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Walker won't rule out wall on Canadian border

John King, Jackie Kucinich and Matt Viser weigh in on the Wisconsin governor's thoughts on a northern-border wall between Canada and the United States.

Walker won't rule out wall on Canadian border

John King, Jackie Kucinich and Matt Viser weigh in on the Wisconsin governor's thoughts on a northern-border wall between Canada and the United States.