Negative spot details allegations about Obama economic adviser's overtures to Canada.
"As Senator Obama was telling one story to Ohio, his campaign was telling a very different story to Canada." Read script here.
Obama's campaign responds, calling the ad contains "flat-out lies" about a "discredited" report.
"What is true is the fact that Senator Clinton said that NAFTA was a victory for her husband...." Read full response and campaign fact sheet.
