There are many crucial items facing the lame-duck Congress, from Ebola to the Islamic State to funding the federal government.

But nobody predicted that the first legislation Congress would take up would be the Mary Landrieu Preservation Act of 2014.

Landrieu, a Democratic senator from Louisiana, is struggling to keep her seat in a runoff next month, and it doesn’t look good: Republican candidates got a combined 56 percent in last week’s election.

So in a last-gasp effort — a Hail Mary, as Capitol Hill reporters were calling it — Landrieu took to the Senate floor as soon as it opened Wednesday after the long fall recess and demanded passage of one of her home state’s pet causes: the Keystone XL oil pipeline, a Republican priority that Democrats have blocked for the last several years because of environmental objections. After taking the floor, she didn’t let it go for most of the next three hours.

“I want to say yes to new majority leader Mitch McConnell,” she proclaimed. “The time to start is now.”

Landrieu made no attempt to hide her motive. “I’m going to do everything in my power here and at home on the campaign trail, where I’m still in a runoff, as you know, to get this project moving forward,” she said.

Republicans were thrilled. Just 40 minutes after Landrieu went to the Senate floor, House GOP leaders announced that they would pass the very same bill on Tuesday — and little surprise. The lead sponsor of the House version of the bill, Rep. Bill Cassidy, R-La., is Landrieu’s opponent in the runoff, and the move would guarantee that he would share credit (and perhaps get his name on the final bill instead of hers).

Suddenly, the full legislative force of the government has been marshaled to try to tilt the results of the Senate runoff in Louisiana. And voters thought lawmakers couldn’t get together to do what’s best for the nation?

Landrieu, upon hearing of the House’s move, exulted on the Senate floor. “Let me just say, hallelujah! I’ll say it again: Hallelujah!”

But the exultant Landrieu had put her fellow Democrats in an awkward spot. Approval of the pipeline was likely to happen eventually, but President Obama could have extracted significant concessions from the Republicans for it. Now they may be giving away that chit for nothing, to aid a colleague in a race she’s unlikely to win anyway. Even if she does, it’s the difference between a 54-to-46 Republican Senate majority and a 53-to-47 majority.

Republicans were ebullient, even before Landrieu’s unilateral concession. McConnell rarely smiles, and when he does it often comes out a grimace, but he was beaming when he posed in his office with 10 newly elected Senate Republicans for a photo op. He used the occasion to condemn President Obama for the climate-change agreement the president struck with China, and he continued to lecture the president when he appeared a couple of hours later on the Senate floor.

Harry Reid, D-Nev., dethroned as majority leader in the next Congress, made a resentful pledge to cooperate with the new majority. “I saw firsthand how a strategy of destruction was debilitating to our system,” he said, clearly referring to McConnell’s time in the minority. “I have no desire to engage in that manner.”

But if Reid was grudging, Landrieu was all in favor of allying with the Republicans, trying to save herself by pushing through the “Hoeven-Landrieu” bill she sponsored with Sen. John Hoeven, R-N.D.

“It needs to get done right now. Not in January. Not in February. Not in March,” she said with the urgency of someone facing a December runoff.

She scheduled a news conference in the Capitol basement, and three dozen reporters and cameramen came to capture the spectacle. “We will pass this in the lame duck,” she predicted.

Under Senate rules, any senator could have blocked a vote on the Keystone measure when Landrieu finally made her “unanimous consent” request Wednesday evening that the Senate vote on the bill next week. Republicans, naturally, didn’t object.

What was more interesting was that Reid and leading liberals, including Barbara Boxer, D-Calif., and Bernie Sanders, an independent from Vermont, were on the floor, but not a single Democrat objected. Apparently, if it takes a pipeline to transport Mary Landrieu back to the Senate, Democrats were willing to build it.

Dana Milbank is a Washington Post columnist.