On a day when Republican presidential candidates stumped for votes in New Hampshire, President Obama paid a visit Tuesday afternoon to the employees of the embattled Environmental Protection Agency, which has been the target of GOP disdain.

Obama joined EPA Administrator Lisa P. Jackson to make brief remarks to an estimated crowd of more than 200 workers, telling them that the environment is safer and the country stronger because of their work.

The EPA has been denounced by Republican presidential candidates as an agency whose dense regulatory requirements have stifled businesses and curtailed economic growth. Last month, Mitt Romney called the agency “a tool in the hands of the president to crush the private enterprise system.”

Obama deflected those attacks. “When I hear folks grumbling about environmental policy, you almost want to do a ‘Back to the Future,’” Obama told the crowd, and remind people “what happened when we didn’t have a strong EPA.” He cited the Chicago River, saying that decades ago one couldn’t “find anything alive in there.”

Yet Republicans aren’t the only ones making EPA employees squirm. In September, Obama abruptly overruled Jackson, pulling back proposed new federal smog regulations that would have compelled states and communities to reduce local air pollution or face federal penalties.

That move, which came in the face of a public relations blitz from businesses opposed to the new standards, angered environmentalists, who feared that the president was allowing politics to trump policy with his reelection campaign in mind.

Obama appeared to refer to that tension obliquely.

“What’s good for the environment can also be good for our economy,” he said. “Now, that doesn’t mean that there aren’t going to be some tensions. That doesn’t mean that there aren’t going to be legitimate debates that take place.”

More recently, Obama won praise from environmentalists when the administration finalized tough new rules to curb emissions of mercury and other toxins from coal-fired utilities. He also delayed a decision on the Keystone XL oil sands pipeline, which Republicans and union leaders have said will create jobs but environmentalists fear will harm natural resources.

In the end, Obama tried to strike a common bond with the workers, commiserating with them over the often long hours they put in at a job that can sometimes appear thankless.

“I know that sometimes spending time getting these policies right means less time at home than you’d like, and you’re missing birthday parties, or you’re missing a soccer game, and the spouse is not happy with you,” the president said, drawing laughs. “I know a little bit about that sometimes. I know these jobs are demanding.”