For anyone watching former attorney general Jody Wilson-Raybould's testimony yesterday, it was hard not to think of Justin Trudeau as another one of those grubby federal politicians from Quebec.

We've seen this movie many times over the years. 

Back in the 1980s, Roch La Salle, a former public works minister in the Mulroney government, resigned in disgrace after being charged with accepting a bribe and influence peddling. Even though La Salle was later acquitted, it finished off his political career.

Another Mulroney cabinet minister from Quebec, André Bissonnette, was investigated for land dealings and eventually charged. He was later acquitted, but his political career ended when he didn't run for reelection in 1988.

Mulroney himself was dogged with charges of blatantly favouring Quebec. This was especially so after his government granted a 20-year maintenance contract for fighter jets to Quebec-based Canadair over a superior bid Bristol Aerospace in Winnipeg.

The premier of Manitoba at the time, Howard Pawley, claimed that Mulroney lied when he said he didn't know what was happening.

That scandal led to the rise of the Reform party and the demise of the federal Progressive Conservatives.

It was later discovered that Mulroney received $300,000 in cash from a dodgy German businessman, Karlheinz Schreiber, who was lobbying on behalf of Airbus. Schreiber wanted Montreal-based Air Canada to buy its planes when Air Canada was a federal Crown corporation under the control of the Mulroney government.

In the late 1990s, another prime minister from Quebec, Jean Chrétien, was dogged by "Shawinigate". A scandal erupted after the National Post reported that he had called the president of the Business Development Bank of Canada to help a businessman finance a hotel upgrade. Chrétien was a shareholder in a nearby golf course.

Less than a decade later during the investigation of the federal Liberal sponsorship scandal, Justice John Gomery described Chrétien as "small-town cheap". Gomery was probing how questionable federal ad contracts were awarded to Quebec firms with ties to the Liberal Party of Canada.

Chrétien subsequently took the commissioner to court and won, but the political damage was done to the Liberal government, ushering in a decade of Conservative rule.

And now, Justin Trudeau has been accused of using the power of the prime minister's office to help get serious criminal charges deferred against a large, Quebec-based construction-services corporation.

Wilson-Raybould mentioned that 11 people from the Trudeau's office, the privy council office, and the finance minister—including Trudeau himself—badgered her or her staff to substitute the prosecution of SNC-Lavalin with a deferred prosecution agreement. This all occurred after Wilson-Raybould had done her due diligence and concluded that she wasn't going to override the decision of the director of public prosecutions.

She described a disturbing conversation that occurred four days after she learned that she was going to lose her job as justice minister. According to her, the clerk of the privy council, Michael Wernick, told her previous deputy minister that "one of the first conversations that the new minister will be expected to have with the prime minister will be on SNC-Lavalin".

This new justice minister, David Lametti, represents a Montreal riding.

So where is this scandal likely to go from here? Here are some possibilities, none of which will enhance the prime minister's likelihood of holding onto power:

1. Trudeau kicks Wilson-Raybould out of caucus

If he does this, she would still likely be reelected as an independent in Vancouver Granville. Conservative and NDP supporters, of which there are many in this riding, would resoundingly support her and she would also retain the support of many previous Liberal voters.

2. Liberal poll numbers crash

It wasn't that long ago that the federal Liberals were the third party in Canada. And that was largely due to the Quebec-based sponsorship scandal and the fact that a former leader, Michael Ignatieff, just didn't connect with Canadians.

His successor as interim leader, Bob Rae, worked extremely hard to bring the Liberals back to respectability. But it was a fragile state of grace, with voters always knowing in the back of their minds that the Liberals had a propensity for dirty dealings. 

Trudeau's actions in the SNC-Lavalin affair are a reminder of those bad old days.

No other prime minister has ever been exposed for lobbying an attorney general against proceeding with a criminal prosecution. It's absolutely shocking to the legal community, which has traditionally been a key pillar of support for the Liberals.

If Liberal popularity falls sharply in the polls, there's a real possibility that some MPs will try to distance themselves from Trudeau.

It's conceivable that some could one day leave the caucus and sit as "independent" Liberals. When caucus revolts reach this level, it's usually a sign that the leader is on his way out the door.

These types of revolts often start with presidents and directors of riding associations speaking out. That would be the first sign.

The next indication would be a series of announcements from Liberal MPs that they're not seeking reelection.

In the meantime, Conservative and NDP nominations will look far more appealing. That increases the likelihood of each of these parties recruiting star candidates before the next election.

Green Leader Elizabeth May may also find it easier to attract high-profile candidates in certain parts of the country.

3. The RCMP launches a criminal investigation of Trudeau

Nobody knows what's gone on over the years between Trudeau and current and former executives of SNC-Lavalin. The prime minister's apparent eagerness to get the company a deferred prosecution agreement could simply be politics—he wanted to help a company with 9,000 employees remain in Quebec. Fair enough.

But what if police decide that there's enough smoke here to warrant a probe to see if there's more to this than meets the eye? If this were to happen, search warrants would be executed, the information to obtain them sit in court registries, and invariably, they would end up in the hands of the media. 

This is perhaps the greatest risk to Trudeau's career. Even if he did nothing wrong, a mere investigation would be enough to undermine public confidence in him and lead to more calls for his resignation.

4. Respected statesmen and stateswomen call for Trudeau's resignation

It's unlikely that the Liberals are going to turn on Trudeau as long as it looks like he has a chance of winning another election.

But pressure could build from outside the party, particularly from former law school deans, former diplomats, former politicians, and former university presidents. If there's a growing chorus of respected voices saying he's has to go, it will make it tougher for Trudeau to win reelection.

5. Trudeau loses his political trump card—his accessibility to the public

If there's one thing that sets Trudeau apart from his predecessor, Stephen Harper, it's his eagerness to interact with the public. We've seen it at Pride parades across the country, in his town-hall meetings, and even when he's on vacation.

But now, if he's dogged with questions about his role in trying to get SNC-Lavalin a deferred prosecution agreement, he may be less likely to want to meet and greet the public. Or when he does, he may face more harassment and heckling, which would defeat the purpose of these encounters.

Trudeau's two main opponents in the upcoming election—Conservative Andrew Scheer and New Democrat Jagmeet Singh—are each far more at ease in meeting with the public than the previous leaders of their parties.

So Trudeau's political trump card, his rapport with average people, is no longer as much of an advantage as it was during the 2015 campaign.

6. Trudeau tries to contain the scandal by firing close associates

By naming so many people in her testimony, Wilson-Raybould has made it harder for Trudeau to pin the blame on one person. She clearly portrayed the clerk of the privy council, a supposedly nonpolitical civil servant, as something of a partisan hack. 

So it will be tempting for Trudeau to fire Michael Wernick and make him the scapegoat if things get too hot in the political kitchen.

But that won't address the role played by several people in Trudeau's office, including his chief of staff, Katie Telford.

In fact, the sum total of Wilson-Raybould's testimony was to suggest that all roads led to Trudeau in the political pressure being imposed on her with regard to SNC-Lavalin. It was Trudeau who demoted her. And it was Trudeau who wanted to discuss SNC-Lavalin with her successor, if Wilson-Raybould's testimony is to be believed.

All of this means that Trudeau can't simply get rid of staff to avoid responsibility. It would just make him look more suspicious in the eyes of the media and the public.

Conclusion

Prime ministers are supposed to represent the national interest and citizens look to them to uphold national values.  Whenever the perception emerges that they don't reflect the values of Canadians or that they strongly favour one region over another, they're finished.

Stephen Harper was perceived to place the interests of Alberta at the front of the line through his rigging of the National Energy Board process to favour pipelines and stifling the legitimate aspirations of First Nations people. Harper's former chief of staff, Nigel Wright, was also involved in some dubious business with Conservative senator Mike Duffy.

Paul Martin lost the 2006 election because the RCMP revealed that it had launched an investigation into the federal finance ministry's handling of income trusts in the midst of a national political campaign.

Jean Chrétien was in deep political trouble, and stepped aside, when it became clear that he was repeatedly helping businesspeople in Quebec, even when they were involved in shady activities.

Brian Mulroney's career was over once the public drew the conclusion that Western Canada didn't matter much to him and that too many of his Quebec cabinet ministers were caught up in scandals.

The albatross around Justin Trudeau's neck is l'affaire SNC-Lavalin. And it's likely to become an even heavier burden as the election approaches.

There was a popular movie released in India this year called The Accidental Prime Minister in which a Sikh politician, Manmohan Singh, unexpectedly rose to the top office in the country.

Don't be surprised if one day, the same term is applied to either Andrew Scheer or Jagmeet Singh.

It would be particularly ironic if Singh were to be the biggest beneficiary of the SNC-Lavalin scandal, given that many in the media have utterly written off his chance of making political inroads in Quebec.

Yet if Singh ends up being judged the "least worst" of the three major party leaders and the most honest, he could indeed become Canada's accidental prime minister, much to everyone's surprise.