The long political battle over the Keystone XL pipeline could reach a pivotal moment this week if enough Democratic senators join Republicans to support a bill that would approve the project, all but guaranteeing a veto showdown with the White House.
And that is an outcome Senate Majority Leader Harry Reid would like to avoid.
That's why many were surprised last week when the Nevada Democrat promised to hold a vote on the issue, defying President Obama's intent to delay a decision on the controversial pipeline that Republicans in Congress almost universally support.
Bypassing the White House would open a new rift among Democrats and be a major step in the complicated political history of the nearly 1,200-mile pipeline, which could one day carry crude oil from the tar sands of Canada to a town in Nebraska en route to the Gulf Coast.
So why is Reid holding a vote on a bill he really doesn't want to pass?
Voting to approve the pipeline would be politically helpful for several conservative-state Democratic senators who are up for re-election this fall, as they try to show voters their independence from the party on the issue.
Eleven Democratic senators, including Sen. Mary Landrieu of Louisiana, Sen. Mark Begich of Alaska, have signed onto the bill. With a guaranteed 45 Republican votes, the Democratic supporters means the measure is awfully close to the 60 votes required to overcome a filibuster threat.
Passage in the Senate would be a milestone, probably prompting swift approval by Republicans in the House. Several years of what have been bitter partisan fights over the mainstays of energy policy -- fossil fuels versus renewable sources, climate change and its deniers -- would come to a momentary bipartisan truce.
But 60 votes is not the same as almost 60, and that may be what Reid is counting on.
A vote of 59 or 58 this week would be a win-win for Democrats. It would allow pro-pipeline senators to show their constituents they tried, while keeping the peace with anti-pipeline senators and environmentalists.
And it would avoid a showdown with the White House that would force Obama to become the vetoer-in-chief.
Sensing the potential outcome, Senate Republicans may not be willing to play the Democrats' game. They have so far panned Democrats' latest offer for a vote on Keystone, as they press other issues as part of a separate energy efficiency bill making its way through the floor proceedings.
A win on Keystone would be a game-changer for the pipeline. A near-win would be business as usual in the Senate.