Tulsa, with a population of about 402,000, is Oklahoma’s second-largest city, and oil and gas are central to its self-image and crucial to its economy, with 20,000 industry jobs in the area. Mr. Bartlett owns Keener Oil & Gas, a family business that was founded in 1910, three years after Oklahoma gained statehood.

Mr. Bartlett spoke of “the old entrepreneurial wildcatter spirit” from those days, when a few men in a coffee shop might hear talk about a gusher, get hold of a nearby lease, secure investors on a handshake and drill. That spirit, he said, continues to permeate the business culture of Tulsa, and of Oklahoma more broadly, where about one in four jobs are estimated to be directly or indirectly tied to the energy industry.

Mr. Pruitt celebrated that kind of frontier capitalism when he ran for attorney general in 2010. “I love the pioneering spirit of our state,” he said in a campaign video.

And in a signal of his antipathy for environmental regulations, he said that government “is not our master, it’s our servant.”

Soon after winning election, he disbanded an environmental protection unit in the attorney general’s office, according to Johnson Grimm-Bridgwater, director of the Oklahoma chapter of the Sierra Club. Mr. Pruitt also established a “federalism unit,” to which he said he would assign state lawyers “to wake up each day and to go to bed each night thinking about ways they could push back against Washington.”

As attorney general, he repeatedly sued the E.P.A. and joined with other Republican attorneys general to fight federal pollution regulations, working hand in hand with the energy industry. In 2014, he sent a letter to the E.P.A. accusing federal regulators of overestimating the pollution caused by gas wells in Oklahoma; the text was written by lawyers for Devon Energy, one of Oklahoma’s biggest oil and gas companies. A billionaire oil executive, Harold G. Hamm, led his re-election campaign.