But E.P.A. officials and independent analysts outside government said that Mr. Perry was claiming credit for improvements in air quality brought in large measure by the very federal laws he has resisted and railed against, and that air pollution in Texas remains worse than in nearly every other state.

“His constituents are benefiting from the Clean Air Act that the E.P.A. is enforcing,” said Janice E. Nolen, assistant vice president for national policy at the American Lung Association. “It’s happening in Texas, but not only in Texas, which tells us that it’s federal action that is responsible.”

David E. Adelman, professor of environmental law at the University of Texas Law School, said the state had made progress in reducing pollution, but still had a long way to go. “For the most part, Texas has lowered its toxic emissions, but so has essentially every other state in the country,” he said, referring to airborne toxins like benzene and butadiene. “The key point to recognize is that Texas started so much higher than everyone else.”

Catherine Frazier, a Perry campaign spokeswoman, said in an e-mailed statement, “If elected president, the governor’s energy priorities will be centered around scaling back the E.P.A.’s intrusive, misguided and job-killing policies, which will empower states to foster their own energy resources without crippling mandates and open the doors for our nation to pursue and strengthen an all-of-the-above energy approach.”

Ms. Frazier said that Texas had achieved large reductions in pollution by following its own path and asserted that some federal actions were driven by politics rather than science.