OTTAWA (Reuters) - Canadian Prime Minister Stephen Harper’s election campaign took another hit on Friday when an opinion poll showed most people do not believe he was unaware of an ethics scandal involving several close confidants.

Canada's Prime Minister Stephen Harper speaks during a campaign stop at the WaterStone Estate and Farms in King Township, Ontario, August 20, 2015. REUTERS/Mark Blinch

The ruling Conservatives, seeking to extend a decade-long hold on power in the Oct. 19 election, are campaigning as a string of awkward revelations arise from the fraud and bribery trial of Senator Mike Duffy, once a close Harper ally.

Harper insists he had no idea his former chief of staff had secretly paid Duffy C$90,000 ($68,700) in 2013 to cover dubious expenses chalked up by Duffy, which are at the heart of the scandal. Evidence at the trial suggests strongly that some of Harper’s top aides knew about the deal.

The Angus Reid poll said 59 percent of Canadians do not believe Harper’s version of events. Almost a quarter of the respondents who identified themselves as leaning towards the right-of-center Conservatives said Harper’s account was untrue.

This could be significant in what looks to be a tight election race. Recent opinion polls show the Conservatives slightly behind the left-leaning New Democrats, who have never governed federally.

Angus Reid said that for 61 percent of respondents, “the Duffy trial points to a deeper scandal within the Prime Minister’s Office and they see it as an unfolding issue that will be key to how this campaign is decided”.

Harper voiced confidence in his current chief of staff, Ray Novak, on Thursday despite court testimony that Novak knew about the secret payment to Duffy.

The trial has heard evidence that senior Harper aides helped concoct a fake story that Duffy had repaid his expenses himself, and that they also directed the Senate, the upper chamber of Parliament, on how to handle the affair.

The revelations are embarrassing for a party that came to power in early 2006 promising to clean up federal politics.

The Globe and Mail, one of Canada’s most influential newspapers, said in an editorial on Friday that “today we are ruled by an imperial prime minister, unaccountable to anyone or anything”.

The newspaper endorsed Harper in the 2011 election.

The Angus Reid online poll of 1,006 Canadians was carried out Aug. 19 and 20. The margin of error is considered to be 3.1 percentage points, 19 times out of 20.

($1=$1.31 Canadian)