The word on the street in D.C. is that passing a clean energy standard will be more difficult than it might appear.

In principle, the idea makes sense as a way to cut through the rancid polarization of energy politics. Set a standard in which utilities must source a minimum percentage of their electricity supply portfolio from "clean" sources. Give the political left renewables, give the political right nuclear.

In principle, a clean standard would let each region focus on its strengths and preferences - solar, wind, and geothermal in the West, onshore wind in the Plains, offshore wind in the Northeast, and nuclear and perhaps biomass in the Southeast.

The eye of the needle could be threaded with legislation that has a fighting chance of securing 60 votes in the Senate and a slapdash majority in the House made up of business-friendly Republicans, blue-dog Democrats, and practical sorts in both parties weary of the bickering that has afflicted energy policy since the president of the United States was in grade school.

Last year, Senator Lindsey Graham (R-South Carolina) floated a clean energy standard bill to get the discussion going. Under his legislation, energy efficiency, renewables, nukes, and any coal plant that could capture and bury 65 percent of its CO2 emissions would qualify for meeting a standard starting at 13 percent in 2012 and ratcheting up to 50 percent by 2050. Graham has indicated he is interested in working on a similar bill in the current Congress.

The difficulties arise in the devil's precincts known as the details. For starters, what does "clean" mean?

Greens wary of any energy source that depends on burning hydrocarbons or splitting atoms are suspicious of the very concept.

Coal-state senators want a baggy definition that leaves plenty of room for keeping coal mines in business and coal trains running while the lab boys in the white coats figure out whether mass carbon sequestration is doable at a reasonable price - a big question mark.

The gas and nuclear industries, plotting on parallel tracks a coup against King Coal, also want a home inside the clean energy tent.

An aide to Senator Jeff Bingaman (D-New Mexico), chairman of the Energy and Natural Resources Committee that would screen clean energy standard legislation, told Energy & Environment News that "designing one large standard that would encompass such diversity is going to be a real challenge," requiring careful modeling to come up with a formula that would both please the various interests and still move the U.S. energy economy away from polluting energy.

Assuming the Senate could figure out those details and pass a bill, it would run into fresh-faced ideologues in the House who worship the golden calf of infallible markets. Anything that smacks of a mandate contradicts their theology that all-knowing, perfectly efficient markets will solve all of America's energy problems.

Which brings to mind a comment from the very same Bingaman aide, who, according to Politico, told a Pew panel discussion: "If you'd told me 10 years ago... that I'd see a day in which oil was $146 a barrel, gas is at 4 bucks a gallon, and we couldn't get a damn thing through Congress on the topic of energy, I'd have said you've got to be crazy. But in fact, that's what happened in the summer of '08."

Three years later, it could be deja vu all over again.