There's a great view from Parliament Hill across the Ottawa River into Quebec.

From their offices, federal politicians can see the beautiful Canadian Museum of Civilization on the opposite shoreline.

Further to the west, stand rows of federal office towers built in the 1970s and '80s, when the government of the day sought to blunt the forces of Quebec separation by ensuring government jobs weren't confined to the Ontario side of the river.

These days, those buildings are about the only signs of a federal presence in Quebec as voters in the province prepare to head to the polls on Tuesday.

Prime Minister Stephen Harper has told his cabinet and caucus to stay out of the campaign. That hands-off decree is in stark contrast, for example, to the Alberta provincial election last spring, when a number of federal cabinet ministers openly endorsed the fledgling Wild Rose Party.

But Quebec is always different. And, this time around, pointedly so.

Recent opinion polls suggest the Liberals under Jean Charest are in deep trouble with voters, especially francophone Quebecers.

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Parti Québécois leader Pauline Marois speaks to reporters while campaigning in Sorel, Que. Ottawa insiders say the Harper government is weighing its options should Marois win the upcoming Quebec election, a worst-case scenario for the federal Conservatives. (Ryan Remiorz/Canadian Press)

The Parti Québécois, out of power since 2003, is solidly back in the picture under Pauline Marois, with a platform that repeats the party's traditional demands for more powers from Ottawa and a promise to hold another referendum on separation as soon as winning conditions exist.

Those same polls suggest a third party, the upstart Coalition Avenir Québec, is enjoying strong support.

The CAQ is led by Francois Legault, a former PQ cabinet minister. But he's vowed not to support a referendum for a decade. His party's platform is focused on the economy, education and health care, all issues that don't put him on a collision course with Ottawa, at least not in the short term.

Taken together, it's a politically unsettled scene, offering no upside for Harper to engage.

Part of the reason is that his party, with just five seats in Quebec, has little organization in the province. And many Conservative policies, such as gun registration and climate change, already run counter to public sentiment. In other words, no sense acting as a lightning rod at the first sound of thunder.

So, ever cautious, Harper has his team working behind the scenes, weighing options, gaming a response depending on the outcome of Tuesday's vote.

'Do we really want to create a crisis that doesn't exist now? We have to wait for the results. Until then, federal politicians need to keep their powder dry.'—Denis Coderre, Montreal Liberal MP

Clearly, a PQ victory is the worst-case scenario for the Conservatives, both politically and economically.

Sovereignty has been dormant as a federal/provincial issue during his three terms in office. A win by the Parti Québécois on Tuesday means having to put every policy through the prism of how it will play in Quebec, of having to deal with the long list of demands in the PQ platform: from control over employment insurance to the right to negotiate international treaties.

Michael Fortier, a former Conservative senator and cabinet minister from Quebec, feels that Harper is up to that challenge.

"In my experience with the prime minister, he's not one that gets hot under the collar and will get caught in any of these traps, if traps are set for him, to create those winning conditions," Fortier told CBC News.

But then there are the financial markets. Harper has spent the past three years promoting Canada as a safe and secure place to invest, a country that is leading all of its G7 partners in recovering from the global recession.

A Marois-led government, with its focus on sovereignty, runs counter to that message. And it underscores a mantra the Conservatives themselves use: the recovery is fragile, any deviation from the path is a threat to realizing that goal.

A silent opposition

The Conservatives aren't the only federal party treading lightly.

The New Democrats hold most of the federal seats in Quebec. More than half the NDP caucus comes from the province, many of them elected just a year ago with the support of soft nationalists and former Bloc Québécois voters.

That's a key reason NDP Leader Tom Mulcair is in no mood to be the federalist voice in this campaign. He's told his Quebec caucus their only role is to vote — while at the same time urging people to look at the shiny object in the window, his promise to have a Quebec wing of his party in place for the next provincial election.

But already questions are being asked about the NDP's Sherbrooke Accord, and its promise to recognize a 50 per cent plus one vote in a referendum — a policy that puts the party at odds with the federal Clarity Act.

If the PQ wins, the other federal parties will try to exploit that position in the rest of Canada — and in the Commons once it resumes.

Even the Liberals are keeping a low profile.

Denis Coderre, MP for the Montreal riding of Bourassa, has been helping some local Liberal candidates in provincial ridings that overlap with his own. But that's it.

He says too many voters remain undecided, making the outcome far from certain, and the mood far too volatile for outside interference to do anything but benefit the Parti Québécois.

"Do we really want to create a crisis that doesn't exist now? We have to wait for the results. Until then, federal politicians need to keep their powder dry."

So, what next?

The Harper government isn't talking publicly, but insiders say his team has been weighing its options, especially if Marois wins.

Michael Fortier is advocating engagement.

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Quebec Liberal Party leader Jean Charest speaks to reporters during a news conference. Polls suggest the Quebec Liberals are in trouble with voters, particularly francophones. (Ryan Remiorz/Canadian Press)

"I think what he needs to do, if …Marois is elected, is to act professionally with her as he has with all the other premiers across Canada. Have his ministers interact with their counterparts ... and try to get things done. I think that is the best way forward and the best way to help federalists in Quebec."

Others argue Ottawa doesn't need to respond to the PQ's demands, even if there is a majority. They argue Marois can win only a narrow majority, with the support of barely more than a third of voters, perhaps, because of vote splitting by the other parties.

They also insist the ballot box question isn't sovereignty, but change after nine years of Liberal governments, complete with allegations of scandal and corruption.

The other option, especially if Quebec voters elect a minority government, is to keep the focus firmly on the fragile economic recovery, pushing the case that Quebec's economic woes are best addressed inside Canada, and in co-operation with the federal government.

But even that has its risks. A former Liberal strategist from Quebec says Harper has no Quebec cabinet minister to champion federalism in the province, or to respond to Parti Québécois demands for more powers.

No matter what happens, Harper's response to the Quebec election will be closely scrutinized, perhaps no more closely than inside his own party.

There's a large segment inside the Conservative party — particularly among its Western base — who favour a much tougher approach to Quebec. They're the ones who point out that Harper formed a majority in the last election with just five seats in the province.

It's a hard line even for a prime minister who has not shied away from hard lines in the past.

But if the separatists do return to power Tuesday night, Harper will have to decide who is going to stand up for Canada the morning after.