It’s been more than five years since Congress passed a national energy bill. But that doesn’t mean legislators stopped trying.

There have been four attempts from Democrats to introduce a national renewable energy standard, with no traction at all. And then there was the cap-and-trade bill, which imploded in 2010.

There have also been a slew of Republican bills aimed at stopping EPA coal regulations, preventing new hydraulic fracturing regulations, killing light-bulb efficiency standards and moving forward on the Keystone XL pipeline.

Energy issues have become so partisan in Congress -- largely due to philosophical issues on spending and climate science -- it's nearly impossible to get anything through.

That's what makes the Shaheen-Portman energy efficiency bill so important, according to its backers.

The bill would establish new voluntary national building codes, set up a Department of Energy center for efficiency research, create a rating platform for supply chain efficiency and set energy performance targets at the federal level. All new spending was stripped out of the bill to bring in Republican support.

However, even with strong support from Republicans and Democrats in both chambers, the bill has failed twice due to the same partisan issues that have derailed nearly every other piece of energy legislation. Last year, it was an amendment approving Keystone XL that killed the bill. This fall, it was Senator David Vitter's (R-LA) demand for an Obamacare amendment coupled with the debt ceiling impasse that forced leadership to take the bill off the floor.

The legislation may come up once more before Congress goes on holiday break. Senators Jeanne Shaheen (D-NH) and Rob Portman (R-OH) are carefully gathering a short list of bipartisan amendments that could help create a filibuster-proof majority (60 votes) and encourage Majority Leader Harry Reid (D-NV) to put it back on the floor in early December.

"We've heard from leadership in the House that if we pass it in the Senate, they will take this up. This can get passed by both houses. This is something we can do now, this year,” said Senator Shaheen, speaking at an energy efficiency event today on Capitol Hill sponsored by the Alliance to Save Energy.

However, a third failure could totally halt momentum for any other Congressional action on energy in the coming year, said Shaheen. If supporters feel burned by any attempts to stop the widely supported bill, the chances for any future bipartisan legislation may get even smaller than they already are.

"If we can't do this, it's going to be very difficult to do anything else on energy policy in this country," she said. "Senate leaders think the road to other legislation goes through passing Shaheen-Portman."

The timeline is tight. Once Shaheen and Portman know they have all the votes they need in the Senate, they'll only have a couple weeks after Thanksgiving to get it to the floor. Assuming it passes without the same earlier problems, it will then go to the Republican-controlled House, where there's more hostility toward efficiency.

Speaking to reporters after the event, both Senators Shaheen and Portman expressed confidence in getting the needed votes, assuming the bill could be squeezed in before Congress adjourns.

"The primary roadblock is finding floor time. We've already had good debates, and we took it to the floor earlier," said Portman. When asked about having the needed votes, he said, "I think we do; yeah, we do."

Compared to the activist mobilization around the 2009 climate legislation or the messaging battles around approval of the Keystone XL pipeline, the Shaheen-Portman bill doesn't incite a lot of excitement. But it's one of the only sweeping actions Congress can take right now -- giving it special significance in the energy sector and in the broader policy landscape.

Watch Senator Shaheen explain the ideas behind the efficiency bill: