Democrats are reportedly considering holding a lame-duck vote to force federal approval of the controversial Keystone XL pipeline, which would carry crude oil from Canada's tar sands to Gulf Coast refineries. A party aide told Bloomberg News that the goal is to help the reelection of Louisiana Senator Mary Landrieu, who is facing a runoff with Republican Bill Cassidy in December.

In doing so, Democrats would beat Republicans at their own game. The GOP-controlled Congress is expected to vote to force approval of the pipeline, a move that stands a good chance of drawing enough Democrats to overcome a filibuster. Right now, though, it's unclear just what the bill might look like.

But Democrats would also risk alienating a core constituency—environmentalists, who collectively spent $85 million to protect Democratic seats in the midterms—all to help a senator who's considered a long-shot to retain her seat. And her electoral troubles have less to do with energy policy than her party affiliation. According to exit polling from the Associated Press, a majority of voters cited the health care law as going too far and half strongly disapproved of Obama. While Landrieu distanced herself, Republicans linked her to President Obama throughout the election, claiming in ads that she “supports Barack Obama 97 percent of the time.”

It's doubtful that a last-minute vote on Keystone will help this image. Landrieu has always made clear she supports the pipeline. She passed a bill out of her committee on Energy and Natural Resources and promised to not “give up on Keystone until we get it built.”

“It's genuinely mystifying how Senate Democrats think one vote would turn undecided Louisianans into Landrieu-voting Democrats,” R.L. Miller, cofounder of the grassroots organizing group Climate Hawks Vote, said in an e-mail. “Landrieu got 43% of the vote on November 4 and the Republicans (Cassidy and Maness) got a combined 57%. So it's not a winning tactic. More important, it's a cynical and shortsighted trade of a project with serious climate consequences in the interest of protecting one seat in the minority.”