Story highlights

EPA official Gina McCarthy has been nominated to lead the Environmental Protection Agency

MIT physicist Ernest Moniz chosen to lead the Energy Department

Sylvia Mathews Burwell tapped for Office of Management and Budget leadership

They have their work cut out for them.

President Obama on Monday tapped a scientist, a businesswoman and a longtime environmental administrator to help deal with some of the most contentious issues now facing Americans, including energy, the federal budget and reducing air pollution.

Walmart Foundation chief Sylvia Mathews Burwell was nominated to head the Office of Management and Budget, Ernest Moniz was named to lead the Energy Department, and assistant EPA administrator Gina McCarthy was Obama’s choice for the Environmental Protection Agency.

The stakes for the OMB are especially high now, with Obama engaged in a heated battle with the Republican-led House about the size and shape of the federal government’s budget.

Sylvia Mathews Burwell is currently the head of the Walmart Foundation, the retail chain's charitable organization.

“Sylvia knows her way around a budget,” the president said at Monday’s White House announcement.

McCarthy would succeed Lisa Jackson, who was repeatedly forced to defend her EPA stance favoring tougher federal standards on toxic pollutants and mercury emissions from coal-burning power plants.

Her nomination could be a signal that Obama plans to make climate change a larger part of his environmental agenda.

Moniz has served on the faculty of the Massachusetts Institute of Technology since 1973, with a research focus on energy technology and policy.

“Ernie knows that we can produce more energy and grow our economy while still taking care of our air, our water and our climate,” Obama said.

Burwell faces big challenges in the ongoing budget debate.

The two sides have failed to reach an agreement to avert mandatory, across-the-board spending cuts that took effect Friday. In addition to the cuts – which amount to $85 billion through the next seven months of the current fiscal year – a possible government shutdown looms at the end of this month.

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McCarthy’s nomination got a thumbs up from former Clinton administration EPA chief Carol Browner, who said she has “worked for and with both sides of the aisle to forge common-sense and science-based solutions to protect children, seniors and the public health from dangerous pollution.”

As EPA chief, McCarthy would step into a lion’s den of controversy over proposed anti-pollution regulations. In 2010, Jackson vigorously defended the EPA against legislation that would have stopped the agency from regulating carbon emissions.

She wrote an editorial accusing the bill’s backers of siding with “big oil companies and their lobbyists” in an effort to “take away EPA’s ability to protect the health and welfare of Americans from greenhouse gas pollution.”

The bill was defeated in the Democratic-led Senate.

In the 2012 presidential campaign, GOP candidate Mitt Romney accused Jackson and two other Obama appointees of pursuing policies that drive up gasoline prices. He called for her firing.

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During her 25-year career, McCarthy has worked at the state and local levels, including time as commissioner for the Connecticut Department of Environmental Protection.

She has also worked for Republican governors, including Romney in Massachusetts, where she once directed his environmental policy.

“I played a pretty good role in trying to get Gov. Romney to finally sign the Massachusetts climate change action plan,” she told CNN’s Jim Acosta last March during the Republican primary.

Moniz was Department of Energy undersecretary from 1997 to January 2001, focusing on nuclear weapons stockpile stewardship. He also was the Department of Energy secretary’s special negotiator for Russian nuclear materials disposition programs.

All three of Obama’s nominees must be approved by the Senate before can take their new jobs.

CNN’s Kevin Bohn and Greg Botelho contributed to this report.