The denials were sweeping when Senator Barack Obama’s campaign mobilized last week to refute a report that a senior official had given back-channel reassurances to Canada soft-pedaling Mr. Obama’s tough talk on Nafta.

While campaigning in Ohio, Mr. Obama has harshly criticized the North American Free Trade Agreement, which many Ohioans blame for an exodus of jobs. He agreed last week at a debate with Senator Hillary Rodham Clinton that the United States should consider leaving the pact if it could not be renegotiated.

On Monday, a memorandum surfaced, obtained by The Associated Press, showing that Austan D. Goolsbee, a professor of economics at the University of Chicago who is Mr. Obama’s senior economic policy adviser, met officials last month at the Canadian consulate in Chicago.

According to the writer of the memorandum, Joseph De Mora, a political and economic affairs consular officer, Professor Goolsbee assured them that Mr. Obama’s protectionist stand on the trail was “more reflective of political maneuvering than policy.”