Keith Johnson at The Wall Street Journal’s Environmental Capital blog picked up the Ceres/NRDC report, making him one of the few journalists to base an article (or blog post as it were) on a comparison of the two climate bills. Still, because the report did not explicitly mention the safety valve or how it factored into the equations, the Journal entry didn’t either. “The gas tax is something that will affect people within the next four months,” Fleming said when asked about the dearth of coverage, “The safety valve is a complicated issue that won’t come into play until at least 2012.”

An article in E&E Publishing’s recently launched ClimateWire news service seems to be one of only two media accounts to dedicate their entire length to the subject (the other came from the Marketplace radio show last October). It is a long and fascinating account of the thirty-year history of the safety valve concept. It didn’t start with climate, but has evolved over the last decade to fit the mold. In 1997, the Clinton administration considered adding a safety-valve clause to the U.S. position at the U.N. climate negotiations that led to the Kyoto Protocol. It was dropped, however, after the idea met strong criticism from environmentalists. Bush thought about including a safety valve after his campaign pledge to regulate carbon dioxide, but he eventually abandoned regulation entirely.

McCain rejected a proposal to include a safety valve in the 2003 Climate Stewardship Act he sponsored with Lieberman. A year later, however, the National Commission on Energy Policy, a bipartisan coalition of industry, environmental, and political representatives, recommended that one be added to any cap-and-trade scheme in order to make it politically feasible (i.e. acceptable to industry and consumers). Apparently heeding that advice, Bingaman did exactly that when he pitched his draft legislation to Republican senators, including Specter, in 2005. Since then, debate has raged, pitting environmentalists, who think safety valves cripple climate legislation, against industry, which thinks having the failsafe is the only way to make cap-and-trade work.

It’s unclear what Obama and Clinton think. Yesterday, Grist’s David Roberts had an interesting Q&A with Jason Grumet, a climate and energy adviser to the Obama campaign who is also executive director of the National Commission on Energy Policy, which authored the 2004 report promoting the safety valve. Roberts notes as much in his introduction, but then, somehow, the safety valve doesn’t come up in the ensuing conversation. The interview is still well worth a read, but it’s too bad that contentious, but central element of the cap-and-trade legislation was once more overlooked, especially given the intense national interest in the gas-tax holiday.

Last month, Grumet sat on a panel in Washington, D.C., sponsored by the Society of Environmental Journalists, with representatives from the Clinton and McCain camps to “debate” the candidates’ green credentials. According to Darren Samuelsohn, who authored ClimateWire’s notable piece on the safety valve and attended the event, the subject of a mechanism to check runaway emissions prices did not come up. “It’s not been a factor in the presidential race,” Samuelsohn wrote in an e-mail. “Maybe when we get to the general, but it’s down in the weeds for the candidates for sure.”

Perhaps that would be different now, in the wake of the gas-tax debate-a reporter could very reasonably stand up and ask Clinton (assuming she stays in the race), “You support pricing mechanisms to bring down the cost of gas; would you support them to bring down the cost electricity?” And beyond that, what’s better-the simple, $12 safety valve ingrained in the Bingaman-Specter bill, or the Federal Reserve-like oversight board described in Lieberman-Warner? And what about other important facets of cap-and-trade: to what extent should credits be auctioned rather than allotted; should initial allotments to companies be based on their current emissions or the amount of electricity they produce; and how will the system play out in regulated versus unregulated electricity markets? Sooner or later we will have to know where the candidates stand.

Correction: An earlier version of this story mistakenly stated that Obama, Clinton and McCain all support the Lieberman-Warner climate bill. In fact, they all support some form of cap-and-trade legislation and only Clinton has specifically backed the Lieberman-Warner bill.

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Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.