Cap and trade was born in 1990 during the administration of President George Bush as a centerpiece of amendments to the 1970 Clean Air Act. Conceived as a business-friendly way to cut pollution without heavy-handed regulation, the idea was that the cap would ratchet down each year, allowing less pollution while market forces drive up the price of permits, creating an incentive for industries to invest in lower-polluting sources of energy. In 2006 in California, Mr. Schwarzenegger signed a pioneering state cap-and-trade law. As the Republican presidential nominee in 2008, Senator John McCain of Arizona pledged to put in effect a nationwide cap-and-trade law.
Officials with the northeastern regional cap-and-trade program that Mr. Romney initially endorsed have played a significant role in shaping the new rule. In frequent trips to Washington over the last several months they have consulted with Ms. McCarthy and other top E.P.A. officials.
People familiar with the drafting of the rule said that after it is unveiled they expect many states to comply by joining the northeastern program, in part because the system has already been designed and tested.
“It’s a plug and play,” said Kelly Speakes-Backman, a commissioner of the regional program. “We’re finding that’s attractive to people. We’ve had states from all over the country calling up and asking, ‘How does this work, and how can it work for us?’ ” The regional program has proved fairly effective: Between 2005-12, according to program officials, power-plant pollution in the northeastern states it covered dropped 40 percent, even as the states raised $1.6 billion in new revenue.