Last Monday night, when environmentalist activists staged 280 candlelight vigils in 49 states to protest the proposed Keystone XL pipeline—in Washington, D.C., demonstrators inflated a giant black tube in front of the White House—many no doubt wondered if their long campaign to halt the project had reached a turning point.

"When I saw the photos coming in from the vigils happening all over the country, I looked at my husband and said, 'We have a real movement here,'" said Jane Klebb, who runs Bold Nebraska, a local group opposing the project.

The previous Friday, the State Department had released its final environmental impact assessment of Keystone XL, which would carry heavy oil from Canada's tar sands across Nebraska and five