Documents are central to the controversy, as is the question of how much information he was provided by his staff. Court affidavits are picked apart by reporters. Calls for an inquiry echo throughout question period.
"The current prime minister owes it to the institution he represents to shed some light on this issue," says the Liberal leader.
But here's the thing — Harper does call an inquiry that examines the inner workings of his own office, and even hosts a 30-minute news conference to answer questions about the brewing scandal and reams of court documents.
No, it's what happened in 2008, when German businessman Karlheinz Schreiber alleged he struck a deal with former Conservative prime minister Brian Mulroney to do defence lobbying work.
Mulroney denied that the deal was struck while he was still in office, but admitted to receiving $225,000 in cash payments.
Harper was drawn in when court documents filed in 2007 showed Schreiber had written letters to Harper that spelled out his allegations against Mulroney. Schreiber also alleged that Mulroney had come to the businessman's defence during a visit to Harper's summer home in 2006, which Harper and Mulroney also denied.
"Obviously, I'm taking this action to protect the position of the Prime Minister's Office," Harper told the news conference that day in announcing the inquiry. "It's important that we have the facts."
Days later, the RCMP said they were also investigating the Schreiber-Mulroney affair. No charges were ever laid.
Fast-forward to 2013, and witness Harper's very different approach to a scandal that this time has engulfed his closest staff and political allies.
Harper has deflected calls for an inquiry into an alleged deal struck inside his office to reimburse Sen. Mike Duffy's contested living expenses. Duffy and Harper's former chief of staff, Nigel Wright, face RCMP allegations of fraud, bribery and breach of trust. No charges have been laid.
Unlike in 2008, Harper has not held a news conference to deal exclusively with the scandal.
Keith Beardsley, a former aide to Harper who worked inside the office at the time of the Schreiber controversy, said pains were taken to quickly retrieve documents and get to the bottom of what happened, thereby taking some of the sting out of the story.
Back then, though, the Conservatives had only a minority government, he added.
"I think at this point, they've gone into the bunker and they're not coming out if they can help it," Beardsley said.
"It was much more proactive before, and right now it seems to be entirely reactive. They sit and wait for something to happen, and then they decide how they're going to handle it once they see it."
In the Mulroney-Schreiber affair, there was no evidence that Harper had actually seen or knew about Schreiber's letters and their content. The inquiry uncovered some weaknesses in how the Prime Minister's Office and Privy Council Office exchanged information.
Harper's approach to protecting the integrity of the PMO now appears to be the polar opposite of 2007, said NDP MP Pat Martin, the party's main critic at the time.
"It's go to ground, deny everything, and rely on that plausible deniability," Martin said.
"Of course back in 2006-2007, they were still using words like transparency and accountability. That seems to have been shed from the vernacular of the PMO as well."
Three years later, one piece of controversial research commissioned for the inquiry, presided over by Justice Jeffrey Oliphant, stands out. Retired University of Manitoba political science professor Paul Thomas set about studying how the Prime Minister's Office and Privy Council Office managed correspondence.
Thomas's research touched on the pitfalls of "plausible deniability," on the rules around record-keeping in the government, the lack of proper training for political staff, and the culture of the PMO.
"Some prime ministers will want as much information as possible; others will prefer not to know certain things," Thomas wrote in a draft of his final research paper.
"To a large extent, it is the prime minister who shapes the culture and climate of the PMO. If the tone set at the top is that there must be no mistakes or problems that embarrass the prime minister, then the likelihood is greater that attempts will be made to manipulate information and lessen vulnerability by covering up problems."
In the case of the current scandal, Harper has said he had no prior knowledge of the payment to Duffy. Six top Tories knew about Wright's payment, and more knew about the efforts to reach a deal with the embattled senator.
Those close to Harper at the time derided Thomas's research as unbalanced, ill-supported by the facts and not based on interviews with staff members who were around the prime minister at the time.
"No one is arguing for plausible deniability, the paper cites no authority that the Government of Canada practises plausible deniability, and in fact the ethic of the current government is accountability not deniability," former chief of staff Guy Giorno wrote in an official PMO response in 2009.
Some took issue with Thomas's suggestion that often young political staff lack the necessary training to grasp the workings of the machinery of government.
"Exempt staff are not free agents making it up as they go along," wrote former Harper adviser and University of Calgary professor Tom Flanagan. "They work in a highly structured environment that sets well-defined limits on what they do."
Beardsley says things were different then, when there were a greater number of older hands around Harper with years of experience in politics.
A recent RCMP affidavit filed in court included emails that provided a window into the interplay between Wright and number of subordinates.
Only one political staff member in the Senate with a decade's worth of experience balked at alleged directions coming from the Prime Minister's Office to water down a Senate report into Duffy and get involved in an independent audit into Duffy's expenses.
"I think the biggest problem this time around is that you were dealing with very inexperienced exempt staff," Beardsley said.
"These are not veteran staff...these are not long-time staff who have a lot of experience in different positions and know what's right and what's wrong."
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