Washington (CNN) - A razor close vote is expected in the Senate Thursday on a Republican amendment to bypass the Obama administration's objections and approve the Keystone XL pipeline, Senate aides from both parties told CNN. Democratic aides, however, expressed some optimism the provision would be defeated.
President Obama lobbied wavering Democrats by phone to shore up Democratic support for his position, a senior Democratic source told CNN. It could be embarrassing for the White House if a large number of Democrats voted to overturn the administration's Keystone policy, which has been hotly debated as gas prices continue to rise during this election year. Several Democrats, including moderates up for re-election and those from oil producing states, support the Keystone pipeline but are torn whether to split with the president.
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Congressional Republicans blasted the president for twisting arms of fellow Democrats.
"By personally lobbying against the Keystone pipeline, it means the President of the United States is lobbying for sending North American energy to China and lobbying against American jobs," House Speaker John Boehner, R-Ohio, said at a news conference.
To make matters more difficult for the administration, Democratic aides said reports last week that former President Bill Clinton came out in favor of building the pipeline are making it harder for Democratic senators to oppose it.
The measure needs 60 votes to pass which means, with Republican Sen. Mark Kirk of Illinois out sick, Republicans will need to pick up 14 Democratic votes for the amendment to pass.
A vote is expected sometime after 4 p.m.