Prime Minister Stephen Harper is losing the credibility battle.

Just over a week after embattled senator Mike Duffy broke his silence on the Senate expense scandal and began implicating the PMO, a new poll shows Canadians are believing Duffy over Harper at a rate of two to one.

An EKOS poll released Tuesday shows that 40 per cent of Canadians believe Duffy's account that he was "coerced by Harper" into accepting a $90,000 cheque from the prime minister's former chief of staff Nigel Wright to repay housing expense claims.

Duffy has characterized the fiasco as a "fake pay back scheme" and "monstrous fraud."

By contrast, only 18 per cent believe Harper's account that he was "unaware of any cheque" and that Wright acted alone. EKOS polled 1,377 Canadians between Oct. 26 and 29. The poll showed that 91 per cent of Canadians are following the scandal either "very closely" or "somewhat closely."

The poll numbers come after an explosive week and a half on the Hill that heard Duffy and his lawyer describe -- citing e-mails, phone conversations and personal meetings -- a PMO-designed scheme that sought to sweep aside questions about Duffy's Senate expenses. Duffy claims the expenses were legitimate but politically inconvenient for the prime minister, because they unnerved the Conservative base.

The stunning revelations -- along with a trickle of documents Duffy has begun to table on the affair -- have put Harper on an endless defensive and revealed cracks in his version of the events, including just how many people within the PMO knew about the cheque. First, Harper said it was just Wright. Last week, he said it was "very few."

Still, Harper denies he knew anything about the cheque and has continued to cast blame on Duffy, who appears to have successfully turned himself from villain to victim in a matter of days.

Earnscliffe lobbyist and former NDP strategist Robin Sears said the change in public perception can be partly attributed to the fact that Duffy has started defending himself after months of silence and because Harper has lost credibility after changing details of his story.

"People have really good bullshit detectors," Sears said. "The Canadian public are very good at judging authenticity and when they watch the PM and his mini-me's make the claims they are making, they just don't look credible."

Duffy has bolstered his credibility, Sears said, by appearing to be armed with a cache of evidence and allegations against the PMO.

"When you throw someone under the bus," Sears said, "you better make sure they're dead."

The only hope for the prime minister and his party, Sears said, is to make some admission of wrongdoing.

"Come clean on everything," he said, "or risk the prospect of the PM being cross-examined by Duffy's lawyers six months from now."

But not everyone is convinced that Duffy has won for good the court of public opinion. Laura Peck, vice president of media consulting firm McLoughlin Media, said that the affair was a fast evolving, "fluid" one that could see Duffy losing the PR battle next week.

"The PM has a majority government and he's going to the convention this week, so that's going to tell another story next week," Peck said. She said the government was doing a good job of promoting the Canada Europe Free Trade Agreement and continuing to focus on the economy.

Still, Peck admitted that the charismatic Duffy has put on a stellar performance in recent days, captivating an audience that remembers him fondly from decades of TV reporting.

"He told a very compelling story," Peck said. "It certainly is not nice… it's cringeworthy, it's sad, it's destructive, it's not good for anybody… but Duffy is telling his story like the good journalist that he was."

Still, she said, no matter who you believe, the story is getting worse.

"Everyday it's like opening up an onion and it smells and it makes you want to cry."

Olesia Plokhii reports for iPolitics, where this article first appeared.