"Nations have no permanent friends or allies; they only have permanent interests." So declared Lord Palmerston, a durable British prime minister of the 19th century.

A French president, Gen. Charles de Gaulle, sang the same song in his time. As le grand Charles told Clementine Churchill, "France has no friends, only interests."

Could all this have something to do with Justin Trudeau's emerging fondness for Conservative ideas?

In election campaigns, of course, parties must claim to be vastly different from the nincompoops they hope to replace. Different on taxes! Different on the environment! Different on health! Different on everything!

Once in office, though, they seem to differ little on Canada's enduring interests. So it is that Stephen Harper's modest targets for reducing greenhouse gas emissions now exert a strange appeal upon the not-so-different Liberals. And, once painted as parsimonious, Harper's health-care budget is suddenly portrayed as equally prudent.

Citing both miraculous conversions on Tuesday, NDP Leader Thomas Mulcair demanded of Trudeau, "Was this always the Liberal plan? Attack Stephen Harper's policies to get elected and then, once in government, adopt those exact same policies?"

Take the GST. Please.

Jean Chrétien and the Liberals campaigned against NAFTA in 1993, then embraced the trade deal once in power. (Tom Hanson/Canadian Press) Trudeau side-stepped and talked about his different style of "co-operation and collaboration." But there's no way around it. Conservative or Liberal, governments do tend to agree, even when it's embarrassing to do so, on what the nation's real interests are.

Remember NAFTA? Why, Brian Mulroney's Conservatives would surely burn in hell for that betrayal of the nation's future, according to Jean Chrétien's Liberals. But, once Chrétien took power, the Liberals embraced it.



And the GST? That, too, was the devil's work until it wasn't. In Opposition, the Chrétien Liberals swore to "kill, scrap and abolish" Mulroney's hated tax. Check your bill. It's still there.



Now, another Conservative scheme has become a national interest in the eyes of the Liberals: a gigantic Malaysian investment in B.C.'s natural gas, which, if built, would increase the carbon emissions the Liberals have sworn to reduce.

That was then. This is now.

But maybe the government thinks it will never be completed — and that wouldn't be crazy. The Pacific NorthWest LNG project, led by Malaysia's national oil company, Petronas, could be derailed by lawsuits, blockades and sagging markets. Natural gas prices have swooned since the plan was announced by Prime Minister Najib Razak during Stephen Harper's visit to Kuala Lumpur in 2013.

But there's really no dispute between Liberals and Conservatives that $36 billion in foreign investment is a splendid thing. It certainly looks like a national interest.

But, but ... didn't Justin Trudeau once tweet that "the Great Bear Rainforest is no place for a pipeline?" Indeed, he did, in 2013. "Too many communities and too many jobs would be put at risk," he added.

The Great Bear Rainforest is no place for a pipeline. Too many communities and too many jobs would be put at risk. <a href="https://twitter.com/hashtag/northerngateway?src=hash">#northerngateway</a> —@JustinTrudeau

Prime Minister Stephen Harper follows Chinese President Hu Jintao, centre, on their way to the official photograph at the Asia Pacific Economic Co-operation summit in Hanoi, Vietnam, in 2006. (The Canadian Press) Trudeau also added the hashtag #northerngateway , but that didn't stop Tom Mulcair on Wednesday from painting it as a flip-flop and demanding of the Liberals, "Is this what you meant when you talked about real change?"

But one must respect tradition, and spectacular flip-flops are woven into our national life. We've only just said goodbye to another traditionalist — Stephen Harper — who had an unrecognized talent for pirouetting like a Trudeau.

In Opposition, for example, Harper damned the quest for "the almighty dollar" in China. In office, he led the chase. In 2008, he campaigned on a carbon cap-and-trade plan, then mocked it in 2011. And, as the Great Recession loomed, he vowed, "We're not running a deficit ... that's our policy. We're not going into deficit." Weeks later, his first whopper of a deficit was in the works.

Even so, do flip-flops rate as capital crimes among the many sins that politicians may commit?

Beware foolish consistency!

Maybe it's not wicked to abandon today the terrible idea you had yesterday — or to ditch a dumb election promise in favour of an enduring national interest. Exactly what that is, of course, is a debatable and flexible concept. But, as John Maynard Keynes famously remarked, "When the facts change, I change my mind. What do you do, sir?"

Or, as Ralph Waldo Emerson had it, "A foolish consistency is the hobgoblin of little minds."

See? At least you can't accuse the Trudeau Liberals of being mired in consistency.