"I don't think many people will vote on the basis of this issue," says Nelson Wiseman, a political science professor at the University of Toronto.
Nor does he feel Trudeau's new perspective will force the Conservatives to reconsider their own position going into the next election.
"To win an election, you don't have to win public opinion — you just have to win 38 per cent of it," says Wiseman, referring to the percentage of the popular vote that Harper's Conservatives took in the 2008 and 2011 elections.
Still, Donald McPherson, executive director of the Canadian Drug Policy Coalition, a national advocacy group that wants to scale back the drug war rhetoric, likens Trudeau's reconsideration of his party's pot policy to U.S. President Barack Obama's "evolution" on same-sex marriage.
"That was a gutsy move," McPherson says of Obama. "But he'd figured it out, he'd read the polls, he took the plunge."
"I can't speculate if this will get any votes for Trudeau or not, but I suspect he'll get more votes than lose them on this one, just because of strong public opinion," says McPherson.
He also suggests that Trudeau's new position "paints Harper as a stodgy old, dyed-in-the-wool conservative who refuses to accept reality."
Late last week, the federal Liberal leader told a rally in Kelowna, B.C. that legalizing marijuana is "one of the only ways to keep it out of the hands of our kids, because the current war on drugs, the current model is not working.
"We have to use evidence and science to make sure we're moving forward on that," he went on.
The immediate political response was unequivocal.
The Conservative Party has vigorously opposed legalization and, after two earlier tries died on the parliamentary order paper, finally passed a law a year ago that sets mandatory minimum prison sentences for pot possession, depending on circumstances.
Justice Minister Peter Mackay said, "I would think Mr. Trudeau should look at other areas in which we can end violence and drug use and end this societal ill."
A post on the Conservative Party web site said the fact "that one of Justin Trudeau's first policy priorities is legalizing marijuana demonstrates once again that he does not have the judgment to be prime minister."
Meanwhile, the NDP, which has long advocated decriminalizing marijuana, called Trudeau's announcement "political pandering."
"He's moved around on the issue quite a bit," says Libby Davies, NDP MP for Vancouver East. She also noted that, as a rookie MP, Trudeau voted in favour of C-15, the first attempt by the Harper Conservatives to establish minimum sentences for possession of marijuana.
She says Canadians "have to look at his consistency, or lack thereof, and determine what his actual position is."
The NDP favours decriminalization, which would remove the risk of arrest for possession of small amounts of pot, because it would give legislators an opportunity to review the outcome and plan a regulatory framework before potentially proceeding to full legalization, Davies says.
The debate over the legalization of pot is a recurring theme in Canadian politics. The Liberal government under Jean Chretien introduced a bill to decriminalize marijuana in 2003, but it failed to pass.
But the response to Trudeau's announcement demonstrates the divisiveness of the issue.
When CBC News contacted the Manning Centre, a conservative think tank based in Calgary, for a response, a spokesperson emailed back to say "we won't be commenting on that issue."
Trudeau's announcement looks to capitalize on a number of factors, says Dana Larsen, director of the non-profit group Sensible B.C., which is campaigning for a provincial referendum on marijuana decriminalization in 2014.
The first is an increasingly relaxed public attitude to marijuana. An Angus Reid poll done last fall found 57 per cent of Canadians support legalization.
The second is growing liberalization in the U.S., where 19 states have legalized the use of medical marijuana and two — Washington and Colorado — recently voted in favour of fully legalizing the drug.
"The number one reason that Canadian politicians have said that Canada won't change on marijuana has been, 'Well, we can't do anything until the U.S. has done it. They'll close the borders, they'll get upset with us,'" notes McPherson at the Canadian Drug Policy Coalition. "That reason is now questionable."
For her part, the NDP's Davies believes that taking a more progressive stance on marijuana can be a vote-getter. "I think there's a very strong public policy to get on with this, and develop public policies based on rational evidence," she says.
But while he applauds Trudeau's current position, Sensible B.C.'s Larsen remains guarded about whether the Liberal leader will follow through.
"The question will be whether he continues to talk about this. It's easy to say stuff when you're in third place."
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