CHICAGO (By Michael Luo, NYTimes) March 4, 2008 — 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.”

It also said the professor had assured the Canadians that Mr. Obama’s language “should be viewed as more about political positioning than a clear articulation of policy plans.”

Campaign officials said the memorandum inaccurately described Professor Goolsbee’s comments, as well as Mr. Obama’s position.

“At no point did anyone in our campaign convey to anyone that there had been any backing away from Obama’s position on NAFTA,” a campaign spokesman, Bill Burton, said Monday.

Mr. De Mora did not respond to requests for an interview, nor did Professor Goolsbee, who campaign officials said was unavailable for comment.

Nevertheless, the controversy, which drew fierce attacks from Mrs. Clinton and Senator John McCain, the likely Republican nominee, put Mr. Obama’s campaign on the defensive at a crucial moment. He and Mrs. Clinton are locked in a tight battle for the Ohio primary on Tuesday.

The memorandum exposed Mr. Obama to accusations of hypocrisy on a touchstone issue, although Mrs. Clinton and Mr. Obama have engaged in posturing on NAFTA as they scrapped for votes in Ohio. The two have used language that has been much more hostile in tone on free trade than the nuanced positions that they had staked out in the past.

The memorandum raises questions about the transparency and the ability of the campaign to address problems before they grow.

The controversy began last week when CTV, a Canadian television network, reported that an Obama official had called the Canadian ambassador in Washington to play down the significance of Mr. Obama’s criticism of NAFTA.

The campaign and the Canadian Embassy issued denials that were, it appears, technically accurate. But they were incomplete because they did not address Mr. Goolsbee’s meeting with Canadian officials.

When WKYC-TV in Ohio asked Mr. Obama about the CTV report, he said: “I don’t have to clarify it. The Canadian Embassy already clarified it by saying the story was not true. And our office has said the story was not. And so I think it’s important for viewers to understand that it was not true.” When pressed, he said, “It did not happen.”

ABC News then reported that the NAFTA conversation involved the Canadian consul general in Chicago, Georges Rioux, not the ambassador. ABC News identified Professor Goolsbee as the official who met the Canadians.

Mr. Burton issued another strong denial, although he declined to respond to a question about Professor Goolsbee’s discussions with Canadian officials.

The spokesman focused instead on the CTV report and attacks from Mrs. Clinton’s campaign based on it.

“Again, this story is not true,” Mr. Burton said. “There was no one at any level of our campaign, at any point, anywhere, who said or otherwise implied Obama was backing away from his consistent position on trade.”

When the memorandum emerged, it confirmed the meeting and that NAFTA was discussed.

According to The A.P., the note reads, “On NAFTA Goolsbee suggested that Obama is less about fundamentally changing the agreement and more in favor of strengthening/clarifying language on labor mobility and environment and trying to establish these as more ‘core’ principles of the agreement.”

On Monday, Mr. Burton stood by his earlier statements, adding that the policy articulated in the memorandum does not contradict anything that Mr. Obama has said on NAFTA in the campaign.

Mr. Obama reiterated that point at a news conference in San Antonio, saying he favors free trade but wants to renegotiate existing agreements to include safeguards for the environment and labor rights.

But in Ohio, his tone has been harsher. In the debate in Cleveland, he agreed with Mrs. Clinton that he would leave NAFTA unless it was renegotiated in terms more favorable to American workers. Mrs. Clinton, who has also found herself on the defensive about positive comments she has made about NAFTA, has stoked the controversy.

When asked about his past denials, Mr. Obama said he had responded with what he knew.

“That was the information I had at the time,” he said.

He added that the Canadians had reached out to Professor Goolsbee and that he met them as a “courtesy.”

“At some point,” he added, “they started talking about trade and NAFTA, and the Canadian Embassy confirmed that he said exactly what I have been saying on the campaign trail.” Campaign officials said Professor Goolsbee went to the consulate as a professor, not as an adviser to Mr. Obama and that other campaign officials did not know about the meeting when it was held.

In a statement, the Canadian Embassy in Washington suggested that the consulate had sought out Professor Goolsbee specifically because of his ties to Mr. Obama’s campaign.

“The Canadian Embassy and our consulates general,” the statement said, “regularly contact those involved in all of the presidential campaigns and, periodically, report on these contacts to interested officials.

“There was no intention to convey, in any way, that Senator Obama and his campaign team were taking a different position in public from views expressed in private, including about NAFTA.”