Barack Obama was forced onto the defensive at the weekend over unguarded comments he made about small-town voters across the midwest.
Obama was caught in an uncharacteristic moment of loose language. Referring to working-class voters in old industrial towns decimated by job losses, the presidential hopeful said: "They get bitter, they cling to guns or religion or antipathy to people who aren't like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations."
The comments were seized on by his rival for the Democratic party candidacy, Hillary Clinton, who saw in them the hope of reviving her flagging campaign by turning voters in the important Pennsylvania primary on April 22 against what she classed as Obama's revealed "elitism".
"I was taken aback by the demeaning remarks Senator Obama made about people in small-town America," she said on Saturday. "His remarks are elitist and out of touch." Clinton campaigners in North Carolina handed out stickers saying: "I'm not bitter."
Obama's comments are potentially incendiary in the Pennsylvania rust belt. Analysts speculated that the remarks could give white working-class voters the excuse they needed not to vote for Obama, whose candidacy has been regarded with scepticism in the state but had shown some signs of growing momentum.
The comments came to light as a result of the Huffington Post's groundbreaking experiment in citizen journalism, Off The Bus. The website runs a network of about 1,800 unpaid researchers, interviewers and writers.
One of those writers, Mayhill Fowler, broke the story, despite being a paid-up supporter of Obama. She attended a fundraising event in San Francisco on April 6 and recorded Obama's speech.
Fowler sat on the material for days, conflicted about what to do with it. She only published the comments last Friday.
"She had some real reservations about the story as an Obama supporter," Amanda Michel, the director of Off The Bus, told the Guardian. "But she thought as a citizen journalist she had a duty to report the event, despite her support for Barack Obama."
Obama initially reacted to the resultant media firestorm over the weekend by trying to stand by his comments. But he later apologised, saying: "If I worded things in a way that made people offended, I deeply regret that."
Clinton will now hope the controversy will provide her with the break she desperately needs in Pennsylvania. She requires a substantial win to sustain her campaign, but recent polls have suggested Obama had eroded some of her advantage.