Some sobering realities, however, were setting in the following day.
The biggest downer for pipeline enthusiasts came in news from Burma. That's where the White House hinted during a press briefing early Thursday, during President Barack Obama's trip to Asia, that he might veto the bill.
A spokesman noted Obama's long-standing view that the legal right to approve cross-border infrastructure belongs to the administration — not to members of Congress.
He noted that the president had scuttled such a congressional effort in the past, and could do it again if Congress tries forcing the issue before the administration completes its ongoing review into the Alberta-to-Texas project.
"I think it's fair to say that our dim view of these kinds of proposals has not changed," Josh Earnest said, while refusing to offer a firm answer on whether there would be a veto.
"There have been previous proposals ... and in evaluating those earlier proposals, we have indicated that the president's senior advisers at the White House would recommend that he veto legislation like that. That does continue to be our position."
He was weighing in after a dramatic flurry of legislative activity the previous day. Two opponents in a Louisiana runoff election used their respective seats in the House of Representatives and the Senate to push companion pro-Keystone bills, with the key vote expected next Tuesday.
If the legislation passes both chambers, and gets Obama's signature, it becomes law. But there are potential pitfalls that could prevent progress on the pipeline.
Here are some of them.
— The Veto: A bill needs two-thirds support in Congress to override a presidential veto — which is 67 votes in the 100-seat Senate. The bill being pushed by Louisiana's embattled Sen. Mary Landrieu does not have those votes.
There's already huge pressure on Obama from environmental groups to veto it, on the logic that he'd be tarnishing his own legacy on climate change by allowing the pipeline just after striking a historic emissions deal with China.
One columnist in the Washington Post pointed to another concern: the bill starves Obama of valuable leverage he might prefer using in two months.
The next Congress, to be sworn in early next year, will be dominated by Republicans. One of their biggest policy priorities — perhaps even their No. 1 issue — is pushing Obama to approve the pipeline. In exchange for that kind of political victory, Obama might have insisted on something in return from the Republicans.
—The Legal Issues: The pipeline doesn't even have an approved route, at least not for now. In Nebraska, the courts have thrown out the existing route, declaring that the state's Republican governor used unconstitutional methods to approve it.
The case is before the state's Supreme Court. Dave Domina, the lawyer fighting the pipeline on behalf of holdout Nebraska landowners, said he expects a decision by the state Supreme Court soon, possibly by the holidays.
Domina said lawmakers need to remember not only that there's a gap in the route in Nebraska but also that the final decision belongs to the president, not Congress.
A hasty move in Washington could prompt more lawsuits, he suggested.
"I would hope people who are looking at these kinds of possibilities don't get carried away with foolish decisions that aren't researched," Domina said. "This isn't all about politics."
—The Filibuster: It takes 60 votes to overcome a filibuster in the Senate. Landrieu has said she thinks she has those votes. Other estimates put the guaranteed support at around 58 votes.
In any case, that tight margin suggests there might be some frantic arm-twisting and vote-counting early next week. The House is expected to pass the bill easily but the Senate vote, expected Tuesday, will be a squeaker.
—The Weather: It's cold outside, and getting colder. Given that the ground is frozen and the construction season is over, it's not an ideal time to be building a pipeline.
TransCanada Corp. says it can build throughout the year, but past statements from workers and from the Canadian government suggest there are meteorological realities to deal with, and union crews in Nebraska say their season starts in the spring.
By next spring, a verdict will probably be out in the Nebraska court case. The Obama administration would then have lost its stated reason for failing to complete its State Department-led review.
And should the administration fail to approve the pipeline, a new Republican-dominated, bitumen-friendly Congress will have been sworn in, with more than enough votes to put another bill on Obama's desk.
Note to readers: This is a corrected story. An earlier version said a bill needs three-fifths support in Congress to override a presidential veto.
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