TO THOSE who believe that the partisan warfare dominating Congress is merely the result of a healthy clash of ideas, we present to you the sad low point the Senate hit on Monday.

For years, seemingly everyone in Congress has agreed that the country should waste less energy and that the federal government has a larger role to play in promoting efficiency. Sen. Rob Portman (R-Ohio) and Sen. Jeanne Shaheen (D-N.H.) wrote a modest, bipartisan bill that would help with that. It eschewed radical policy. Lawmakers from both parties got input. Congress-watchers kept the bill on the short list of things legislators might actually manage to send to President Obama. Yet on Monday the bill failed on a largely party-line vote.

That means, for now, that the federal government will not be required to push through upgrades to energy-gobbling computer systems, or to tighten model building codes to reduce the unconscionable amount of energy buildings waste, or to demand that federally backed home mortgages account for energy efficiency in the appraisal and underwriting process. Manufacturers, meanwhile, will not have stronger incentives to use energy-efficient electric motors and transformers.

These failed proposals were timid. A stronger plan would have required states to improve their building codes rather than just give them a better model code from which to work. The bill could also have been more creative: One proposal called for investing in a Race-to-the-Top-style plan that would have encouraged states to compete on energy reductions. Instead, Portman-Shaheen was least-common-denominator policy.

But all the careful watering-down could not save this consensus bill from partisan sabotage. Though many GOP senators had extensive influence on the shape of the bill, Republicans sought to add a slew of energy-related amendments on the floor — on divisive issues such as Environmental Protection Agency rules and natural gas exports. Democrats didn’t want to risk dooming the bill by attaching amendments that would have split their caucus or provoked a presidential veto. Senate Majority Leader Harry M. Reid (D-Nev.) refused to allow votes on these sorts of changes. Enough Republicans, including several co-sponsors, bolted from the bill that it failed to obtain the 60 votes necessary to overcome a filibuster.

Mr. Reid should not have denied his fellow senators the opportunity to vote freely on energy policies when considering an energy bill, even if the debate would have been politically inconvenient. But once he refused to allow minority amendments, Republicans should have voted on the merits of the policy before them. Democrats wonder whether Republicans’ underlying motivation was to deny Ms. Shaheen an election-year victory. That’s very possible, just as it’s very possible that Mr. Reid cared more about saving Democrats from taking politically difficult votes than about advancing decent policy. But the other explanation for the GOP’s behavior — that Republicans petulantly filibustered after losing a procedural disagreement — is hardly any better.