If  you want to understand why the Democrats suffered such losses at the hands of midterm voters—and why one Democrat remains likely to be punished by the voters of her state—you must look no further than yesterday’s Senate vote on the Keystone XL pipeline.

Despite having time and again gotten a clean bill of health on an endless array of environmental studies, the Keystone XL pipeline was filibustered by Senate Democrats and defeated by one vote. This was a particular blow to Louisiana Senator Mary Landrieu, a Democrat, who introduced the bill and hoped it might save her Senate seat. The embattled Ms. Landrieu faces a runoff with Republican Bill Cassidy next month. She introduced the bill to show that she has clout and understands energy. But, as the Washington Times explains, environmentalists were not about to help save Landrieu’s seat:

The Keystone vote took on symbolism far beyond the small impact on American crude supplies and the slight effect expected on gas prices. Environmentalists drew lines and dared moderate and conservative Democrats to cross it. In the end, most were unwilling to defy the ascendant movement, and it marked a key moment in the climate change debate.

It is a key moment demonstrating the power of the unappeasable environmental movement, many of whose leaders have trust funds and thus aren’t overly moved by the prospect of the jobs the pipeline would create from American citizens, but it doesn’t necessarily bode well in the long run for them.

In the very short run, the bill will come up again in the Republican-controlled Congress early next year. It will almost certainly pass. Then there is the question of overriding the inevitable presidential veto. The president will justify his veto by claiming that this studied to death project needs yet more studies.

In the long run, however, this vote could be remembered as one in which Democrats lined up behind an environmental movement that is not swayed by scientific studies and puts its weight behind defeating projects that can create employment in safe, environmentally-respectful ways. So Mary Landrieu wasn’t the only loser yesterday–and hers is not the only job likely being lost, at least for the time being, by this vote.