Senate Democrats are working on plans to hold a vote authorizing construction of the Keystone XL pipeline -- approval that Democrats believe might bolster the chances of Sen. Mary Landrieu (D-La.), who faces a tough runoff election next month.

It was not immediately clear Tuesday night whether Republicans would consent to proceeding with such a vote during the lame-duck session that begins on Wednesday -- especially given the high stakes surrounding Landrieu's reelection race. Such a move would also draw howls from the environmental movement who had hoped that President Obama would resolve a years-long dispute over a long-awaited energy project in their favor.

Several Senate Democratic aides confirmed on Tuesday evening that talks are underway to allow for a vote authorizing construction of the pipeline in the coming days. The aides, who were not authorized to speak publicly on the matter, said that details on language of the bill authorizing and its timing were not yet settled, but likely would be among the topics of conversation as Congress reconvenes Wednesday.

Landrieu is expected to make a formal announcement of plans to hold a vote later Tuesday or on Wednesday, the aides said.

Landrieu faces Rep. Bill Cassidy (R-La.) in a Dec. 6 runoff to determine who will take the last remaining Senate seat still up for grabs. Throughout her campaign, she has touted her chairmanship of the Senate Energy Committee and her strong support of her state's energy industry as one of the reasons why Louisianans should reelect her. But ever since Republicans retook control of the Senate, Cassidy and his allies have emphasized that Landrieu's clout no longer matters now that the GOP is poised to control the Senate next year.

And just because Democrats plan to hold a vote doesn't guarantee that the plan will succeed: Majority Leader Harry M. Reid (D-Nev.) attempted to hold a vote earlier this year to authorize construction of the pipeline, but Republicans blocked it as they sought votes on unrelated matters.

Citing that failed attempt to hold a vote, Brooke Hougesen, a spokeswoman for the National Republican Senatorial Campaign Committee, criticized the Democrats' emerging plans in an e-mail to reporters on Tuesday night.

"They say that when you’re in a hole you should stop digging, but Harry Reid hasn’t learned his lesson," she wrote. "Democrats tried the same strategy outlined below earlier this year in a failed effort to protect Kay Hagan, Mark Udall, and Mark Pryor from voters in their states. It didn’t help them, and it won’t help Mary Landrieu."

News of plans to hold a vote was first reported on Tuesday by Bloomberg News.

Obama has made clear he plans to take his time on Keystone -- close advisers oppose the pipeline -- and congressional Democrats have showed little enthusiasm for the pipeline in the past. But the idea has gained steam in recent days in a bid to help Landrieu.

Before Election Day, Landrieu cited Obama's opposition to constructing the pipeline as one of the reasons why she was struggling to win reelection.

"One of the main reasons is because his energy policies are really different than ours," Landrieu said of Obama in an interview with NBC's "Meet the Press." "I mean, we're a pro-production state. We wanna drill almost anywhere. People believe that it's an opportunity for Americans to become energy self-sufficient."

The oil industry has championed construction of the pipeline, which would transport oil from tar sands of Canada to the Gulf of Mexico, while the environment movement has seen it at something that would contribute to harmful emissions of greenhouse gases.

For Senate Democrats, the move might be low cost. Republicans have long made clear they would seek to approve the Keystone XL pipeline if they won power of Congress. Since last week's elections, there has been intense speculation about whether Obama might concede Keystone to Republicans, perhaps in exchange for something he wants.

In a recent interview, Sen. Bob Corker (R-Tenn.) cited the Keystone project as one example of ways that his party could work with Democrats.

"It’s not the biggest thing ever to be deal with -- it’s just the destructive way it’s been dealt with has become symbolic," he said of the pipeline project.

Sen. Heidi Heitkamp (D-N.D.), who cited Corker as one of her closest GOP colleagues, also cited the Keystone project as an easy issue to resolve next year.

"I just think that there’s tons of things that the American public expects us to do and not all of them are big, big things. But I think we should get to work doing them," she said in an interview.

Even if Congress doesn't act, Keystone seems to have at least some support from the State Department, which is currently reviewing the border-crossing pipeline to determine whether it is in the "national interest" -- a process that has dragged on for several years.  Obama has warned that the pipeline will only be approved if it "does not significantly exacerbate the problem of carbon pollution."

The State Department's research, however, has tended to lean pro-pipeline. In its final supplemental environmental impact statement released early this year, for instance, it suggested that Keystone probably wouldn't increase global greenhouse gas emissions, and further, outlined scenarios of what might happen if Keystone is not built, noting in particular that "rail will likely be able to accommodate new production if new pipelines are delayed or not constructed." Indeed, the report showed that more and more oil from Canada is already being transported in this way:

Growth of crude oil transported by rail from the Western Canadian Sedimentary Basin. Source: Department of State, Final Supplemental Environmental Impact Statement for the Keystone XL Pipeline .

Why's that significant?

The State Department suggested in its report that if the crude oil that Keystone is meant to carry were to travel by rail instead, the result might be higher greenhouse gas emissions and a greater likelihood of spills. Environmental groups were very critical, but the point is that even before the shift in control of Congress, one important arbiter of Keystone's fate seemed to have laid out much of the evidence you need to make the "pro" case.

But there's yet another hurdle -- a case before the Nebraska Supreme Courtover the pipeline, which has arisen over an attempt by the state's legislature to let the governor approve the pipeline, which a lower court then ruled unconstitutional. The higher court's ruling could either speed the pipeline forward, or provide yet another of many roadblocks.