On a 55-36 vote, the Senate fell short of the 60 votes needed Monday to move ahead on the innocuous and popular efficiency bill from Sens. Jeanne Shaheen (D-N.H.) and Rob Portman (R-Ohio) that had been caught in the headwinds of the far more politically fraught debates over the Keystone pipeline and EPA regulations.

In the end, Monday’s vote appeared to have little connection to fights over energy policy and more to do with Republicans’ running complaints that Senate Majority Leader Harry Reid has ruled the chamber with an iron fist, preventing them from debating amendments to a host of bills.

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The vote wasn’t directly linked to the Keystone pipeline. All the Democrats present for the vote, including several who favor approving the pipeline, supported Reid’s procedural move to block Republican amendments on Keystone, EPA greenhouse gas restrictions, a carbon tax and expediting liquefied natural gas exports.

The election-year maneuvering was hard to miss.

Sen. Mary Landrieu (D-La.), a co-sponsor of the bill who is in a tough reelection fight, was the first to speak on the floor, where she heaped blame on Republicans again for missing the chance to get a vote on Keystone by killing the efficiency measure.

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Landrieu again cited her ascension to the chair of the Senate energy committee while taking aim at another vulnerable incumbent in a tight race — Senate Minority Leader Mitch McConnell.

“So as chair, I intend to be as fair as I can be with both parties, and putting things on this floor that we can be proud of, together. Everybody gives a little, takes a little and gives a little, we move forward,” she said. “That is not enough for the Republican leader. The Republican leader wants an issue, he does not want the pipeline. I hope the people of Kentucky will remind him how important the pipeline is.”

Landrieu’s early campaign ads have highlighted her new position atop the energy committee in her reelection, although Republicans have sought to turn that against her by arguing she is still powerless to get Reid to hold votes on items important to her state’s oil and gas industry, including the Keystone pipeline.

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Her challenger, Rep. Bill Cassidy (R-La.), quickly put out a press release headlined, “Landrieu’s ‘Influence’ Fades on Keystone.”

Three Republican co-sponsors of the efficiency bill — Portman, Susan Collins of Maine and Kelly Ayotte of New Hampshire — sided with Democrats to back Monday’s cloture vote.

Three other GOP co-sponsors of the bill — John Hoeven of North Dakota, Johnny Isakson of Georgia and Roger Wicker of Mississippi — voted against limiting debate without additional Republican energy amendments.

“At this point, we’re not going to agree to shut off amendments. Either we keep on working to get something or not. That’s up to the majority leader,” Hoeven told POLITICO shortly before the vote.

Reid in the end switched his vote to ‘no’ to allow the energy efficiency measure to be brought up again.

But that seems unlikely, since he and McConnell are once again blaming each other for allowing another bipartisan bill fall by the wayside.

McConnell sought unsuccessfully to hold votes on a slew of amendments, and then trimmed his request to just five Republican proposals, including a measure to pre-empt EPA greenhouse gas restrictions for power plants that is opposed by coal supporters in his state. Reid objected to both attempts.

At the start of Monday’s session, Reid argued from the Senate floor that voting to limit debate on the Shaheen-Portman bill would be a “fresh start” for a Senate that has been dogged by gridlock.

But Portman, while voting in support of Reid’s procedural move, spoke in favor of allowing his fellow Republicans to attach a handful of energy amendments.

“It’s a reasonable request and wish it could be granted,” he told reporters shortly before the failed vote.

He also vowed to continue talks.

“At this point, [there are] not enough votes to get cloture,” Portman said. “But on the other hand, the negotiation is pretty close and so I’m hoping it would be reconsidered and we can maybe take a breather … and reconsider just having four or five votes on amendments.”

Next up on the Senate floor are tax extenders. Portman said Republicans will also ask for a full debate, perhaps setting up another impasse.

“Republicans will insist on it, just as they did on energy efficiency,” Portman said to reporters.

Alex Guillen contributed to this report.