A pair of senators stumped to revive energy-efficiency legislation on Wednesday, suggesting its failure would prove a bellwether for future energy bills in the upper chamber.

Sen. Jeanne Shaheen, D-N.H., recalled a recent conversation with the Senate Committee on Energy's leaders in which they said the efficiency bill she is co-sponsoring with Sen. Rob Portman, R-Ohio, was a litmus test for all other energy legislation.

The bill is rather innocuous — it would establish voluntary efficiency standards for building codes, bolster efficiency by manufacturers and encourage the federal government to use less energy, among other things. The House has indicated it would take up the bill if the Senate can pass it.

But it's been a long time -- 2007, to be exact -- since a substantive bill has cleared the upper chamber. That's turned the bill into a free-for-all for amendments, which could range from a vote on the Keystone XL oil sands pipeline to whether the Environmental Protection Agency should regulate greenhouse gas emissions, that threaten its passage.

"The road to additional energy policy goes through passing Shaheen-Portman. If we can't do this, then it's going to be very difficult to do anything else around energy policy in the Senate," Shaheen said the Energy Committee's top lawmakers, Chairman Ron Wyden, D-Ore., and ranking member Lisa Murkowski, R-Alaska, told her. Shaheen was speaking at a Washington event hosted by the Alliance to Save Energy.

The bill's journey to the Senate floor, which dates back to last legislative session, has been arduous.

Senate Majority Leader Harry Reid, D-Nev., finally put the bill on the docket in September. But he yanked it when Sen. David Vitter, R-La., pushed an amendment to force executive branch employees and congressional staff to participate in the Obamacare health exchanges, inciting anger from Democrats who said it was an improper place for such a measure.

Time is running out for the legislative session, but Shaheen and Portman have been working on a new strategy to get the bill to the floor.

They're working with colleagues on a set of bipartisan amendments to put into the bill's text —and then reintroduce it — in hopes of securing a filibuster-proof 60 supporters. Shaheen said they're "close" to that goal, although she declined to tell reporters how close.

The plan, if it comes to fruition, would help disarm amendments like those from Vitter, Portman told reporters on the sidelines of the event.

"We're working on that. We're making good progress. We have a little more ways to go to get the numbers that we would like, but we think once we have that we are going to go back to leadership," Shaheen said.

"The fact is, we learned a lot from the earlier effort," she added.