Presidential candidates don’t usually squabble over underground infrastructure. So how did the proposed $7 billion Keystone XL pipeline become the biggest environmental issue of the election?

SEPTEMBER 2008: Energy company TransCanada applies for a U.S. permit to build Keystone XL.

FEBRUARY 2009: The State Department launches an environmental-impact study with Cardno Entrix—a consulting firm hired by Trans-Canada in the past. 

AUGUST 2011: The study finds that Keystone will have “no material impact” on the environment.

NOVEMBER 2011: Some 12,000 protesters encircle the White House. Days later, President Obama postpones his decision and requests further environmental review.

NOVEMBER 2011: Republican lawmakers introduce legislation aimed at forcing Obama to make a decision on Keystone.

JANUARY 2012: The president rejects TransCanada’s application; Mitt Romney refers to the pipeline for the first time, slamming Obama.

FEBRUARY 2012: TransCanada announces that it will split the pipeline in two and build the section from Oklahoma to Texas, which doesn’t require a permit to cross the U.S. border.

MARCH 2012: Obama fast-tracks the southern leg of the pipeline, boasting that his administration has laid enough pipeline “to circle the earth.”

APRIL 2012: Romney tells an Arizona crowd that he will “build that pipeline if I have to do it myself.”

NOVEMBER 2012: THE RETURNS ARE IN!
Whether Obama or Romney wins may hardly matter: insiders say the pipeline will probably happen either way in early 2013. If he’s reelected, chances are Obama will let the second environmental-impact study run its course, then approve a plan, albeit with conditions. (He could, say, tie it to new vehicle emissions regulations.) And if Romney is elected? Despite his campaign promises, he can’t make Keystone his first order of business. He, too, will have to wait for the study.