"Yesterday's announcement demonstrated that in one year we were able to do what, in ten years, the previous government was unable to do," Justin Trudeau declared with his first opportunity during question period Wednesday.

Most of the Liberals in attendance stood and cheered.

It's of course a bit early to unfurl the "Mission Accomplished" banner.

Strictly speaking, the Liberals didn't break new ground Tuesday when Trudeau announced his approval of two pipelines, including one that would carry oil from Alberta to the coast of British Columbia.

Two years ago, the Conservatives approved the Northern Gateway project. This week, the Liberals approved the Trans Mountain pipeline.

It was just the actual building of a major pipeline to tidewater that eluded Stephen Harper's government, along with U.S. President Barack Obama's rejection of the Keystone XL pipeline.

President-elect Donald Trump might be willing to approve Keystone, but it will be up to Trudeau to overcome the opposition and obstacles that come with building a pipeline to the coast.

But while Trudeau confronts profound questions about Indigenous rights, social licence, humanity's dependence on oil and the potentially disastrous consequences of climate change, his political opponents in the House of Commons are at least providing him ample space to sound like the moderate voice of reason and compromise.

That merely leaves him with the task of doing two controversial things at once: building a pipeline and putting a price on carbon.

Conservatives see glass one-third empty

Trudeau approved two pipelines Tuesday, but the Conservative focus is on the fact he also scuttled the Northern Gateway project (which the Federal Court had already ruled against because the Harper government failed to meet its constitutional obligation to consult with Indigenous communities).

So the glass, as the Conservatives see it, is one-third empty.

The Conservatives believe as many pipelines as possible should be approved and loudly championed. Meanwhile, they've shown little interest in meeting Canada's international targets for reducing greenhouse gas emissions — particularly not with anything resembling a price on carbon.

After Trudeau's announcement, Ambrose was left to argue the prime minister will prove incapable of overcoming local opposition to get Trans Mountain built. On Wednesday, she began challenging Trudeau to go to B.C. and make his case.

"Mr. Speaker, a press conference does not build a pipeline," she said, perhaps citing one of Confucius' lesser known aphorisms. "When is he going to go out to British Columbia and convince the very people who oppose this pipeline to get on board?"

Interim Conservative Leader Rona Ambrose doesn't think Trudeau has the ability to overcome public opposition and get the Trans Mountain project built. (Sean Kilpatrick/Canadian Press)

That's not an unreasonable request — even if the approval of Northern Gateway in 2014 was announced with nothing more than a news release and setting aside the unsuccessful example of Stephen Harper's pipeline diplomacy.

But the cynic might venture that the Conservatives' best hope is that Trudeau fails.

NDP's internal struggle

The New Democrats, meanwhile, must contend with internal tensions.

While Leader Tom Mulcair was declaring on Tuesday that the prime minister had "misled" British Columbians, Alberta Premier Rachel Notley was hailing Trudeau's leadership. And while the only NDP government in Canada desperately wants a pipeline, the Leap Manifesto suggests a hasty move away from oil.

Trudeau and Alberta NDP Premier Rachel Notley shake hands during a meeting on Parliament Hill Tuesday after the federal cabinet approved Kinder Morgan's Trans Mountain expansion. (Justin Tang/Canadian Press)

The federal NDP doesn't categorically oppose the construction of pipelines, but it has yet to find a pipeline it's willing to support.

New Democrats support action on climate change and would cut emissions deeper and faster than the Liberals.

In the present case, NDP MPs can pursue Trudeau on questions of process — whether Indigenous communities were sufficiently consulted and how the prime minister can account for having told an activist the Trans Mountain review process would be redone.

But as he accused Trudeau of betrayal on Wednesday, Mulcair set the prime minister up for a counterpunch.

"Can the prime minister honestly tell them that things would have been different if Stephen Harper were still in power?" Mulcair asked on behalf of disappointed B.C. residents.

The prime minister stood and answered with a list of differences: a new price on carbon, new regulations to protect the B.C. coast and federal co-operation with the provinces to reduce greenhouse gas emissions.

Trudeau in the middle

At one point during question period, Conservative MP Mark Strahl stood and insisted the relevant science made the case for Northern Gateway, just as it did for Trans Mountain. Shortly thereafter, NDP MP Linda Duncan stood and explained that the science proved Trans Mountain to be a bad idea.

The realist might argue that everything in a democracy is an inexact science.

"One side of the House wants us to approve everything and ignore Indigenous communities and environmental responsibilities," Trudeau said Tuesday afternoon, beginning the Goldilocks defence he's used for other issues. "The other side of the House does not care about the jobs or the economic growth that comes with getting our resources to market."

On the one hand, that might leave the Liberals to satisfy some mass of voters who don't like the sounds of that choice.

On the other, the Liberals could be pulled apart by the competing forces.

Beyond the House of Commons, Trudeau will face public pressure and legal challenges.

Paul George protests the Trans Mountain Pipeline expansion project in Vancouver on Tuesday.

"Make no mistake, people power will stop pipelines," environmental group 350.org declared in response to Tuesday's announcement.

The extent of the opposition remains to be seen, but overcoming it and winning re-election is what would enable Trudeau to claim true victory.

To accomplish this, he's trying to sell two big ideas simultaneously: building a pipeline and putting a price on carbon. The thinking being that each can be used to justify the other, even if both are vehemently opposed by some — the theoretical answer to two competing concerns.

That's either the easiest or the hardest pitch to make.