Maine independent Sen. Angus King will vote against approval of the Keystone Pipeline, dealing a blow to Democrat Sen. Mary Landrieu's efforts to pass the legislation Tuesday -- a move intended to bolster her chances of winning a runoff next month to save her seat.
"Congress is not -- nor should it be -- in the business of legislating the approval or disapproval of a construction project," King said in a statement provided to CNN.
"And while I am frustrated that the President has refused to make a decision on the future of the pipeline, I don't believe that short-circuiting the process to circumvent his Administration is in the best interest of the American people. I urge the President to make a decision soon, and, if he doesn't, I look forward to working with Congress to put a timeframe on this decision."
To overcome a filibuster from fellow Democrats, Landrieu must gather 60 votes. As of now, only 59 senators have publicly stated their support for the legislation to circumvent the administration and approve construction of the Keystone Pipeline.
Still, Landrieu told reporters Monday night that she does have 60 votes -- possibly more -- but would not say who has given her private assurances.
Landrieu is hoping that leading the charge to pass the long stalled Keystone Pipeline -- which she argues will create jobs nationwide -- will prove to Louisiana voters that she is a force in Washington that they need. It also helps powerful energy interests in her state.
Monday night King told reporters he was leaning no, but hadn't made a formal decision.
A source close to King tells CNN he did not want to publicly disclose his position until he called Landrieu personally, which he has now done.
Since the vote is not until this evening, King did not want to string people along who have deep interest in the pipeline, which is why he is now publicly stating his opposition.
Another Democrat thought to be a possible yes vote for Landrieu was Sen. Jay Rockefeller of West Virginia, who is retiring at the end of this year. But he told CNN Monday night he too is a no vote.
Even if Landrieu does get 60 votes, it is an open question whether President Barack Obama would sign or veto the bill, since he has publicly opposed this approach for some time.