 -- The controversial Keystone XL oil pipeline failed to win approval in the Senate tonight by one vote, a blow to Louisiana Sen. Mary Landrieu who hoped to be able to push it through.

Landrieu, a Democrat who is in a tight December run-off to keep her Senate seat, was one of the lead sponsors of the bill and had expressed confidence earlier in the day that she and other supporters had rounded up the 60 votes necessary to approve the long stalled project.

The final vote was 59-41.

Shortly after the vote was tallied, Kentucky Sen. Mitch McConnell, who will become the Senate Majority Leader when Republicans take control of the Senate in January, said he will bring up the issue again "early next year."

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“It’s been on my agenda and it’s staying on my agenda and I’m going to do everything I can to help America become energy independent,” Landrieu said after the bill was defeated. “This fight was worth having.”

The vote was a nail-biter as it was unclear whether the measure had support of 60 senators before the vote began. Sens. Dick Durbin, D-Ill., and Chris Coons, D-Del., were two senators considered as potential last minute yes votes, but the two senators voted against the measure.

Landrieu said she “felt relatively certain that the coalition that was put together was strong enough to find the extra one. I say we have to work on our little muscle a little more.”

Fourteen Democrats joined all 45 Republicans in support of the measure. The White House had refrained from announcing whether President Obama would veto the measure, but many Democratic senators expected the president to veto the bill had it passed.

When the vote was called, protesters against the pipeline started shouting in the Senate chamber. The protesters, which included Greg Grey Cloud and Maria Langholz, were escorted out of the Senate chamber.

After two years of inaction on the Keystone XL pipeline measure, the Senate decided last week to vote on the bill at the urging of Landrieu, who is facing a tight December run-off race to maintain her Senate seat.

“I took that opportunity. I called for this vote, not Harry Reid, not Mitch McConnell. I called for it and I think it's worth fighting for,” Landrieu said.

“I’m going to fight for the people of my state until the day that I leave. I hope that will not be soon, so I’m going to continue to shake this place up when I can to identify opportunities as I see them to push an important debate forward for not only Louisiana, not only my part of the country but for the entire country,” Landrieu said.

Last week, the House passed a Keystone bill proposed by her Republican opponent Rep. Bill Cassidy, R-La.

Support for the pipeline has become a significant issue in the Louisiana run-off campaign.

The pipeline would carry oil from Canada's tar sand pits to refineries in the U.S. Opponents of the bill warn that the Keystone pipeline would further damage the environment.

“XL stands for Xtra Lethal and misery follows the tar sands,” Sen. Barbara Boxer, D-Calif., said today.

The White House had not said whether it would veto the legislation if it had passed, but many Democratic senators believe the president will do just that.