WASHINGTON — The U.S. House on Thursday debated a Keystone XL pipeline bill by U.S. Rep. Bill Cassidy as a runup to a vote Friday that is all but certain to call on the White House to greenlight the project — as the House has voted to do more than a half-dozen times before.

Meanwhile, the U.S. Senate incumbent that Cassidy hopes to unseat in the Dec. 6 runoff election in Louisiana, Mary Landrieu, lobbied her fellow Democrats to support an identical Senate version of the legislation.

While that might look like a strikingly unusual example of collaboration among political opponents, it’s actually something far different: a struggle for Keystone bragging rights.

But no matter who gets the credit if the bill clears Congress, the chances of Democratic President Barack Obama signing it into law are virtually nil — and the chances are even less of a veto override before the current session shuts down at year’s end.

“The case for approving the Keystone XL pipeline is clear and obvious,” Cassidy said on the House floor Wednesday. “This is a perfect example of what the American people have asked us to do.”

Cassidy, a three-term House member from Baton Rouge, introduced his version of the Senate Keystone bill this week. It’s been fast-tracked by the ruling House Republican leadership and is set for final passage Friday. Approval is all but certain.

Landrieu is co-sponsor of a Keystone bill by U.S. Sen. John Hoeven, R-N.D., that she moved through the Energy and Natural Resources Committee she chairs in June. But the bill has not come up for a floor vote due to partisan wrangling and objections from a majority of the Democrats, who currently rule the Senate.

As a result of Democratic defeats in Senate elections Nov. 4, that reign will end when the new Congress convenes in January. Landrieu hopes to return then for her fourth term, but she is locked in a tough fight with Cassidy for the seat. Polls show her losing the Dec. 6 runoff.

The pipeline would bring “dirty” tar-sands oil from Canada to refineries on the Texas Gulf Coast. Supporters of the pipeline say it will create jobs and reduce American dependence on oil imported from unfriendly and unstable foreign countries outside North America. Opponents fear it will result in increased carbon emissions, and the project has been stalled by Obama, whose approval is required because the pipeline crosses an international border.

In her campaign against Cassidy, Landrieu has touted the influence she has gained in the Senate by virtue of her seniority. The Democrats’ loss of the majority means she will forfeit her biggest plum — chairmanship of the energy committee — to a Republican, but she still would like to show she can get things done for her state, where support for the pipeline is strong.

On Wednesday, she took to the Senate floor to press for a vote on the Hoeven bill, which directs the White House to approve the project. This time, the Senate Democratic leadership agreed and has set a vote for as early as Tuesday. The movement in the Senate spurred Cassidy into action in the House.

Under the Senate rules for the legislation, it will take 60 votes to pass the bill, meaning Landrieu has to round up 14 additional Democratic votes besides her own to combine with the expected unanimous support of the 45 Republicans.

She is said to be close — maybe a vote or two shy. If both the House and Senate approve identical measures, then the proposal can go directly to the White House, with no need to resolve the differences that are typical in such cases. Landrieu has said she’s OK with having Cassidy’s name on the legislation that wins final passage.

In the House debate Thursday, Majority Whip Steve Scalise, of Jefferson, chimed in to support the Cassidy bill.

“Everything about this says ‘do it,’ says ‘yes,’ ” Scalise said. “Stop saying ‘no’ to American jobs. Stop saying ‘no’ to American energy security.”

Radical environmental extremists have held the bill hostage, Scalise said.

But Rep. Henry Waxman, D-Calif., said opposition was far broader than that.

“The Keystone XL pipeline is a terrible deal for America,” he said. “We get all the risk, while the oil companies reap all the rewards.”

And Rep. Peter DeFazio, D-Ore., said of the Cassidy bill, “It would help a House member defeat a Senate member and get elected to the Senate, so I guess it’s a bad bill whose time has come.”

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