Prime Minister Stephen Harper, the Conservative leader who promised to usher in a new era of accountability when his government came to power in 2006, is seeing his credibility erode following months of controversy surrounding a Senate expense scandal, a new poll suggests.

Harper promised during a speech to his party in Calgary on Friday that the Conservatives will "do the right thing" and suspend senators Patrick Brazeau, Mike Duffy and Pamela Wallin without pay, but new poll numbers suggest his credibility is on par with that of the senators who are under investigation by the RCMP.

"No one has credibility on this issue," said Nik Nanos, president of Nanos Research.

A small fraction of those surveyed, 11 per cent, found Harper to be credible in his defence of the Senate expense scandal, the Nanos poll found. Just over half, 53 per cent, described Harper as not credible.

The rest of the respondents found the credibility of Harper's narrative wavering between somewhat credible to somewhat not credible, or they were unsure.

The Nanos Research survey of 1,000 Canadians was conducted from Oct. 26 to 30, 2013. Participants were randomly recruited by both landline and cellphone, and administered a survey online.

The results were statistically checked and weighted using the latest census data. The margin of error for a random survey of 1,000 Canadians is plus or minus 3.1 percentage points, 19 times out of 20.

Half truths

Senators Brazeau, Duffy and Wallin were no more credible than the prime minister.

Wallin committed fraud and breach of trust by filing inappropriate travel and living expenses inside a three-year period, the RCMP alleged in court documents obtained by CBC News on Friday.

All three former Conservative senators now stand accused of allegedly committing criminal offences.

Under 10 per cent of respondents described the trio as credible — only seven per cent of those surveyed found Wallin credible, compared with five per cent for Duffy, and two per cent for Brazeau.

Of those surveyed, 51 per cent thought Duffy was not credible, compared with 50 per cent for Brazeau and 41 per cent for Wallin.

"Their credibility is at about the same level as Harper's credibility," Nanos said.

"Canadians don't believe anyone. If you ask an average Canadian, they probably think that all of them are speaking a half truth."

Harper has maintained all along he knew nothing about the $90,000 his former chief of staff Nigel Wright gave to Duffy out of his own pocket to repay his ineligible expenses.

Wright's "deception," according to Harper, is the reason why his right-hand man is no longer working for him.

The danger with the prime minister's narrative, Nanos said, is Harper believes it's always "somebody else's fault."

"Yet this is the same prime minister that held to account a minister of the Crown for an $8 glass of orange juice."

Politicians have to be prepared to be judged by the standards that they set and that they expect others to live by … that's why it's so important that he have a clear narrative and clearly explain his role and what he knew in order to try to put this behind him," Nanos said.

The Senate expense scandal may result in a lower voter turnout in the next federal election. The question, Nanos said, is who will benefit from that on election day.