By Sam Youngman and Jeff Mason
EUCLID, Ohio (Reuters) - It was one of the defining moments of the 2008 presidential campaign: A woman at a rally for Republican John McCain, while asking McCain a question, called Democratic contender Barack Obama "an Arab" who couldn't be trusted.
McCain took the microphone and said, "No ma'am. He's a decent family man ... who I just happen to have disagreements with on fundamental issues." McCain's response symbolized his discomfort with the volatile crowds he was seeing as his campaign faded during the final days of the 2008 race.
On Monday, at a factory in this Ohio community near Cleveland the crowd that greeted Mitt Romney wasn't angry, but the Republican presidential candidate faced a similar situation.
A woman asked Romney whether he thought Obama was "operating outside the structure of our Constitution." The woman then added that the president "should be tried for treason."
Romney, who spent much of his appearance criticizing Obama's efforts to create jobs, responded by ignoring that part of the woman's question and focusing on recent comments Obama had made about the U.S. Supreme Court.
After the event, Romney told CNN that he did not agree that Obama should be tried for treason.
"I don't correct all of the questions that get asked of me," he said. "Obviously, I don't agree that he should be tried."
By then, Obama's spin machine was in high gear, accusing Romney of a lack of leadership for not disagreeing with the questioner's accusation of treason.
"Time after time in this campaign, Mitt Romney has had the opportunity to show that he has the fortitude to stand up to hateful and over-the-line rhetoric and time after time, he has failed to do so," Obama campaign spokesman Lis Smith said in a statement.
For Obama's staff the episode, however inflated, was a chance to go on the offensive. Obama's campaign recently has been muted by a diplomatic controversy in China, polls suggesting Romney's ratings were up in some key states, and Vice President Joe Biden's support for same-sex marriage, which highlighted Obama's own reluctance to embrace the idea.
Before Romney's appearance in Ohio, the Obama campaign already had begun to emphasize a new narrative with a video ad that addressed what is likely to be the president's biggest vulnerability: the sluggish economy.
The ad - which will air in nine battleground states - makes a point of saying that Obama inherited a devastated economy, and portrayed the president as leading an American comeback.
(Jeff Mason reported from Washington; Editing by David Lindsey and Christopher Wilson)