Bruce Anderson is the chairman of polling firm Abacus Data, a regular member of CBC The National's "At Issue" panel and a founding partner of i2 Ideas and Issues Advertising. Read more of his weekly columns.

The Prime Minister has spent his week preparing for one of the more important choices he will make in his career in politics. Stephen Harper's decision about what role he wants Canada to play in the fight against the Islamic State is full of peril. On the substance of what action to take, only lousy options are apparent. And the communications stakes are extremely high.

Imagine a message spectrum that runs from provocative and obnoxious on one end, to persuasive and charming on the other. Much of the time, talking points from the Prime Minister's Office are designed to stir party loyalists by fomenting contempt for pretty much everyone else.

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But with a year to go until another election, and trailing in the polls, the Prime Minister seems to want to move the communications needle. It's nothing you could really describe as a campaign to persuade, more like a desire to avoid carelessly annoying voters.

Many were upset at how MP Paul Calandra handled questions about Canada's involvement in Iraq in the House of Commons last week. Chances are nobody was more ticked off than Mr. Harper himself.

I doubt Mr. Harper sees political opportunity in Iraq: he is coming across as more aware of the political risks.

Over the first 30 days of Canada's engagement, he has done little to reduce his risk. He has barely hinted at the choices he's considering or the factors he is weighing. He's sidestepped questions about cost, duration, measures of success.

However, he's done so in a measured, business-like fashion. If he can't bring himself to campaign for more public support for a Canadian mission, at least he seems determined not to squander what support currently exists.

Over recent months, Mr. Harper's muscular foreign policy rhetoric left no way to avoid some type of combat engagement, even if he were tempted to do so.

If he has little room to maneuver on a combat role, Mr. Harper surely knows that public support for air strikes or troops on the ground would be tentative, and conditional.

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There's no room for flippancy when lives are on the line. Most voters who didn't vote for Mr. Harper aren't really outraged at his government– but treating a new military engagement as though it doesn't require any public accountability is the kind of thing that can push them to that point.

That was Mr. Calandra's mistake, and why the consequences were more serious than when he was similarly cavalier in answering questions about the Duffy-Wright affair. If last week's apology wasn't specifically ordered by the Prime Minister, it was almost certainly approved by his office. And this PMO is not exactly known as an apology factory.

Mr. Harper knows victory against the Islamic State will be difficult to define, and even harder to achieve. In contrast, setbacks and costs may accumulate, painfully and publicly.

To compound things, Mr. Harper will be casting his lot with Barack Obama: someone with whom he shares few political values or instincts.

The Islamic State is a threat that is fairly new and lightly known to most Canadians. Mr. Harper may have to endorse a mission of indeterminate length, with goals that sound worryingly inconclusive, more like "degrading an enemy" than "eliminating a threat."

Canadians' support will be contingent on feeling confident in the judgments and trusting of the motives of the government. They will want to know that Mr. Harper is acting in a careful, thoughtful and prudent manner. That he is avoiding, not indulging in, his taste for small-ball partisanship.

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As he prepares to reveal and wear his plan for Canadian involvement, Stephen Harper knows that, practically speaking, there is almost no chance this mission will improve his electoral prospects. And plenty of ways it could have the opposite effect.