WASHINGTON — In November 2010, three combatants gathered in a sleek office here to build a carbon emissions policy that they hoped to sell to the Obama administration.

One was a lawyer who had been wielding the Clean Air Act since his days at the University of California, Berkeley. Another had turned to practicing environmental law and writing federal regulations to curb pollution after spending a summer on a pristine island off Nova Scotia. The third, a climate scientist who is a fixture on Capitol Hill, became an environmentalist because of postcollege backpacking trips in the Rockies.

The three were as seasoned and well connected as Washington’s best-paid lobbyists because of their decades of experience and the relationships they formed in the capital.

Over the next two years the lawyers, David Doniger and David Hawkins, and the scientist, Daniel Lashof, worked with a team of experts to write a 110-page proposal, widely viewed as innovative and audacious, that was aimed at slashing planet-warming carbon pollution from the nation’s coal-fired power plants. On June 2, President Obama proposed a new Environmental Protection Agency rule to curb power plant emissions that used as its blueprint the work of the three men and their team.