The Conservatives made a memorable political play during Super Bowl, 2007, running TV attack ads warning Canadian football fans that Stéphane Dion was not a leader. Now, a day after he was elected to lead the Liberals, Justin Trudeau is being framed in Tory ads that say he's "in way over his head."

The Globe and Mail asked three experts for their thoughts on this type of political messaging. Jonathan Rose is a professor of political science at Queen's University in Kingston, who has written extensively about political advertising. Andrew Owen is a professor at the University of British Columbia who researches public opinion. And David Dunne is a professor of marketing at the Rotman School of Management.

Can the ads backfire, and under what circumstances?

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All three experts said yes and referred to the television ads run by the Progressive Conservatives during the 1993 federal election campaign that targeted Jean Chrétien's facial paralysis.

"They backfire when they focus excessively or exclusively on the personal," Prof. Rose said. "They backfire when their claims aren't plausible. And they backfire when they seem to be outside the norms of propriety."

Prof. Owen said ads must not be seen to have crossed the line of decency. But these days, he said, political parties run their ads by focus groups to make sure that won't happen.

Prof. Dunne said advertising can go wrong if it is not something that people are already inclined to believe. In that case, "there is not likely to be a backlash against them," he said, "but people are likely to ignore them if they don't hit any relevant point."

Does it matter if political attack ads stretch the truth?

Potentially yes, say the experts.

Prof. Rose said many political ads would not pass the Advertising Standards Canada's test of veracity, but their claims should be supportable in some way. In the case of the Trudeau ad, he said, it takes a quote out of context to suggest something that isn't true. "So it doesn't just invite false inference," Prof. Rose said, "it creates a completely wrong impression."

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Prof. Owen said ads that are factually incorrect could be problematic for the advertising party. But those that simply play with the truth are difficult to combat.

And Prof. Dunne said that truth-stretching is really the name of the game with political ads. But it does matter if there is an outright lie, he said, because the other party will make that known through the media.

What should be the strategy of a party that has been the victim of an attack ad?

All experts agreed there must be a response.

Prof. Rose said that, in the case of Mr. Trudeau, the Conservatives are filling in a vacuum of knowledge about his leadership. "Without any evidence to the contrary, these claims seem plausible."

Prof. Dunne said taking he high road can be risky. "So usually what most politicians do is they will attack back," he said. "Essentially what they are doing is deflecting attention and trying to polarize the debate."

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Prof. Owen said research shows that the volume of the ad buy is more important than the content of the ads themselves. So "the short answer is to buy lots of ads" in rebuttal, and not to take on the specific messages of the attack ads but to counter them with alternatives.