The potential choice of McCarthy — a Massachusetts native who led Connecticut’s Department of Environmental Protection from 2004-2009 — would likely draw heavy criticism from Republicans.
GOP lawmakers have made EPA’s emissions rules for power plants and other sources the top focus of attacks on the White House regulatory agenda, alleging the standards are economically burdensome.
The agency has also completed a separate regulation to limit soot- and smog-forming power plant pollution that crosses state lines, although a federal appeals court later tossed out the rule.
McCarthy won Senate confirmation in 2009 for her current job, and would replace former EPA Administrator Lisa Jackson, who left the agency last week after announcing her intention to step down in December.
McCarthy has been rumored for weeks to be the top contender to run EPA, and if confirmed, she could be at the center of a huge second-term environmental battle.
Green groups are strongly urging EPA to move ahead with a plan to set carbon emissions rules for existing power plants, calling it among the most powerful tools that Obama could wield through executive power at a time when climate legislation is frozen in Congress.
While McCarthy has already drawn Republican fire in her current role, she is also a former adviser to Romney, the GOP’s standard-bearer in the 2012 White House race.
Romney was the last of several Massachusetts governors that McCarthy worked under before leading Connecticut’s environmental department.
She was Romney’s under secretary of policy at the Massachusetts Executive Office of Environmental Affairs, and deputy secretary of operations for the cross-cutting Office for Commonwealth Development that Romney created, work that included development of policies on smart growth and climate change.
Another major piece of Obama’s energy and environment team might also fall into place soon.
There is speculation that Obama could be leaning towards nominating Ernest Moniz, a Massachusetts Institute of Technology physicist and veteran of Beltway policy battles, to lead the Energy Department.
Moniz directs MIT’s Energy Initiative and is already among the Obama administration’s outside advisers on energy.
He would replace another physicist, outgoing Energy Secretary Steven Chu, but if confirmed Moniz would arrive with much more Washington experience than his predecessor.
He served as undersecretary of Energy for several years during the Clinton administration and remains a familiar face in Washington, testifying at a number of Capitol Hill hearings through the years.
Moniz is currently a member of the President's Council of Advisors on Science and Technology, and served on the “blue ribbon” commission on nuclear waste policy that Obama created in 2010 and issued a final report a year ago.
—This story was updated at 6 p.m.