If the prime minister has lied to or misled Parliament and Canadians about his role in the Senate expenses scandal, a vast majority of Canadians think he should resign, a new EKOS poll indicates.

As details continue to emerge about which Conservatives were aware of the scheme to repay Senator Mike Duffy’s expense claims – and, as Duffy himself revealed Monday, his legal fees – the stakes are only getting higher for Prime Minister Harper.

Should it be proved Harper was aware of what was going on, which thus far he has denied, 68 per cent of 1,377 Canadians polled from October 26 to 29 think he should step down immediately.

Only 30 per cent agreed his fate should be left to voters in the next federal election.

Since that still remains a hypothetical question, however, it wouldn’t seem to pose a problem, yet.

[start_gallery] [end_gallery] Unfortunately for Harper, though, the court of public opinion isn’t judging him innocent until proven guilty.

While almost two in five Canadians aren’t buying either his or Duffy’s version of events, more than twice as many (40 per cent) believed Duffy than Harper (18 per cent).

Why is Duffy winning the credibility battle? We have that answer here.

And as far as scandals go, Canadians perceive the goings-on in the Senate to be even worse than the Liberal scandal that helped bring the Conservatives to power in 2006.

[start_gallery] [end_gallery]While 65 per cent of Canadians rated the 2004 sponsorship scandal as “very serious” — a number that might well have been affected by the passage of time — 75 per cent of Canadians felt that way about the senate scandal. In comparison to something more recent, 73 per cent described the 2011 Robocalls revelations as “very serious.”

But it gets worse for the Conservatives.

As they gather in Calgary for their convention starting Thursday, they may now have to start considering the impact all this could have on their ability to win the next federal election in 2015.

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Asked whether the senate scandal would affect how they vote, almost half of Canadians (48 per cent) said it would. A trend that extends into the Conservatives’ 2011 voters. Of those who cast a ballot for Stephen Harper’s party in the last election, 29 per cent say this scandal will affect whom they tick a box for the next time around.

University of Toronto history professor Robert Bothwell attributes some of Senate scandal’s resonance to both its simplicity and personalization.

“Scandals need to be simple and if possible, like Watergate, centred around an unlikable personality. But the personalization, regardless of likeability, is what amplifies the effects,” he wrote.

“The prime minister’s credibility is crucial to his electoral success. When the cred drains away, so does the PM’s mandate.”

According to EKOS the poll — which they prefer to call a “hybrid online/telephone research panel” — had an overall margin of error of +/-2.6 percentage points, 19 times out of 20.

Canadians were randomly recruited using landlines, cell phones, and the internet, with equal probability sampling.