As a candidate, Barack Obama envisioned his administration passing a national low-carbon standard. The proposal would have required transportation fuel producers and importers to reduce carbon dioxide emissions from their fuels.
Nearly four years later, the standard does not exist.
In general terms, the proposal would require companies to meet a performance target for the amount of carbon dioxide released during the life of a fuel, from the oil fields to your car's gas tank.
Proponents use the phrase "carbon intensity" as shorthand for the rate of carbon dioxide released per unit of energy. It pertains to more than the fuel itself -- it also refers to carbon dioxide released in the process of producing and importing the fuel. So, technically, even a carbon-less energy source -- electricity as an example -- could have some carbon intensity associated with its production at the power plant.
A target would give companies the latitude to buy credits from companies that specialize in low-carbon biofuels. Companies could also lower their average carbon intensity by increasing the production of other kinds of fuel, such as hydrogen or natural gas.
Obama included the low-carbon standard as one of many ideas to wean the country off foreign oil, promote alternative energy and address climate change concerns.
Joseph Mendelson, policy director for climate and energy at the National Wildlife Federation, said the proposal is rooted in pragmatism: Even if markets for alternatives, such as biofuel or electric, continue to grow, conventional gasoline and diesel are likely to be part of our energy future.
"If you still have fuels around, you want them to be the least carbon polluting fuels possible," Mendelson said.
California and Oregon are the only states to have a low-carbon fuel standard, though most states in the Midwest and Northeast regions have studied the option in the last few years. (You can see a map here showing U.S. states and European countries that have a carbon standard, or are considering it.)
In his campaign promise, Obama said the standard would require fuel companies to reduce their carbon intensity 5 percent by 2015 and 10 percent by 2020.
In 2009, the U.S.House of Representatives, then controlled by Democrats, worked on major climate change legislation that included a national low-carbon fuel standard. But oil companies opposed it, and the final version passed the House without such a standard.
The Senate and House also considered individual bills on establishing a national low-carbon fuel standard in 2009, but both died in committee.
"It failed in large part because no one knew what it was or what it meant," said Dr. Daniel Sperling, director of the Institute of Transportation Studies at the University of California, Davis.
Two foundations, the William and Flora Hewlett Foundation and the Energy Foundation, have given grants to Sperling and other academics to research the proposal, giving special attention to its potential benefits and costs. Their findings, published in July 2012, are available on the group's website, the National Low Carbon Fuel Standard Project.
The White House Office of Science and Technology still mentions a low-carbon fuel standard as part of its environment and energy Website; the standard would be part of the White House plan to reduce greenhouse gas emissions by 80 percent by 2050. But we couldn't find any sign of the administration actively pushing the idea since the climate bill stalled in 2009.
We contacted the White House for any evidence that Obama advocated for the a low-carbon fuel standard, but never heard back.
Some groups say it's not Obama's fault that Congress won't pass legislation.
"(Obama) can't be held at fault for a dysfunctional Congress," said Heather Taylor, the director of a political arm for the pro-environmental reform group, the Natural Resources Defense Council. "He's shown if he could do something, he would."
One of the principles of our Obameter, though, is we rate promises for outcomes, not intentions. So with no low-carbon standard on the horizon, we rate this a Promise Broken.