At least one candidate at Wednesday night's Republican presidential debate saw a downside to the idea of building a fence on the U.S. border to deter the migration of undocumented workers.

Rep. Ron Paul (R-TX) told debate moderators that such a fence could be used against Americans.

"The people that want big fences and guns, sure, we could secure the border," the congressman noted. "A barbed wire fence with machine guns, that would do the trick. I don't believe that is what America is all about."

"Every time you think about this toughness on the border and ID cards and REAL IDs, think it's a penalty against the American people too. I think this fence business is designed and may well be used against us and keep us in. In economic turmoil, the people want to leave with their capital and there's capital controls and there's people controls. Every time you think about the fence, think about the fences being used against us, keeping us in."

Watch this video from MSNBC's Republican Presidential Debate, broadcast Sept. 7, 2011.

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