After a seven-year stalemate, the Obama administration is finally getting around to killing the Keystone XL pipeline.

Keystone would have carried oil from Canada through the Midwest to the Gulf of Mexico. It probably would have created some jobs and limited America's dependence on foreign oil. So why did Obama kill it?

The short answer is he bowed to liberal environmentalists who have long pressured his administration to crush Keystone.

This is unfortunate. Years ago, Obama's own State Department produced an environmental impact statement green-lighting the project. "The central finding in the draft environmental impact statement," The New Yorker's Ryan Lizza told NPR's Terry Gross back in 2013, "was, if you don't build Keystone, the Canadians will sell this stuff anyway, they'll build pipelines to their east coast, to their west coast, and they'll send it to the Gulf of Mexico via rail — and by the way, sending oil by rail releases a whole lot more greenhouse gas emissions than putting it in a pipeline."

This is still true today, even now that Justin Trudeau has become Canada's new prime minister. His new Liberal government backs the pipeline. And he's not exactly happy about Obama killing it.

I'm not the sort of partisan who's spent the last several years agitated about Keystone, as many on both the left and right have. I've always felt that this is just one project; it wouldn't be an enormous job creator, but nor would it be a huge climate killer. Nixing Keystone won't matter much to the environment, and might even be a net negative. And if you're really worked up about climate change, why focus on Keystone? The ultimate game is to get an international agreement (there are talks scheduled in Paris) that would address checks on reducing China's emissions.

But the real Keystone issue, of course, is about the political symbolism. Although both sides exaggerated the potential costs and benefits of Keystone, the issue ultimately serves as a microcosm of President Obama's entire presidency, which has been plagued by increased polarization, acrimony, and gridlock. Given the choice to be a uniter who transcended partisanship, or a partisan who bowed to liberal special interests, Obama — who campaigned as a change agent — has almost always chosen partisanship.

Keystone could have been a bipartisan victory. Free-market conservatives are for it. Liberal-leaning labor unions are for it. It was just the environmental left that opposed it. First Hillary Clinton bowed to them. And now Obama has, too.

Obama ran as a centrist. His refusal to concede even a small victory to Republicans, supported in this cause by labor unions, is indicative of his unilateral and unchivalrous mentality toward the right.

But perhaps most damning of all is the timing of Obama's decision.

In his Friday announcement, the president said Keystone wouldn't really help the U.S. economy and could hurt the environment. Well, okay, maybe so. But that was as true in 2010 as it is today.

Why did Obama wait until nearly six years into his presidency to deal with Keystone? Because his whole wait-and-see approach was a political charade.

Making a decision on Keystone, one way or the other, was always going to cost a Democratic president the ire of a key group: labor unions or the environmental left. By keeping Keystone in a sort of purgatory all these years, Obama effectively avoided angering a key liberal constituency. For instance, look at this blistering statement from a key labor union about Obama's decision today:

We are dismayed and disgusted that the president has once again thrown the members of [The Laborers' International Union of North America], and other hard-working, blue-collar workers under the bus of his vaunted 'legacy,’ while doing little or nothing to make a real difference in global climate change. His actions are shameful. [LIUNA, via The Hill]

That's absolutely brutal criticism for a Democratic president to receive from a labor union. It's no wonder Obama wanted to avoid that in past election years. It's understandable. It's also extraordinarily cynical.

But sadly, it's hardly the first time this president, fueled by politics, took years to publicly "evolve" on an issue...